BGW-210 700 vs 5268AC, which is better?

Neither is better than the other. I’ve never heard of tech support from Europe. Are you sure you were talking to AT&T? What number did you call?

As browndk26 indicates, the BGW210 and 5268AC are roughly equivalent.    And I, too, have never heard of a European call center.

The models were released at different times, with likely different intent within the markets.

First some history Uverse was first deployed in select markets starting in 2006/2007....

Early UVERSE FTTN gateways were the 3600 (no IPTV service) and the 3800 (coax for IPTV service along with supporting Uverse. The 3801 was an improvement on the 3800 offering better stability at longer loop distance. Uverse was initially restricted to about 2500 feet (half mile copper) best speed of 24, the 3801 extended that distance to about 4000 feet with best internet speed of 12.  These were all single pair service with the gateways being 2WIRE manufactured with 2.4Ghz wireless b/g and (4) T100 ethernet ports.

During a portion of this time the MOTOROLA 510 was released for ADSL2+ UVERSE instead of the VDSL models from 2WIRE. The biggest advantage was the 510 had 2.4Ghz b/g/n wireless.

Around 2011 2WIRE 3812 aka iNID was released, this was the first bonded pair gateway... intended for addresses over 3000 feet of copper out to about 5200 feet (1 mile) offering internet 18 with 3HD streams instead of the internet 12 with 2HD streams max from the 3801 at longer distances. Shorter distances under 2200 feet were single pair internet 24 capable, 2200 feet to 3000 feet was single pair best speed of internet 18 while over 3000 feet as bonded also offered internet 18.

In 2013 the Motorola 589 was released, a bonded pair gateway replacing the 2WIRE 3812... the 589 was a smaller, single device instead of the 3 separate devices of the iNID (outdoor unit) with iPSU (power supply unit) and i38HG (indoor unit that provided internet service). It was after the release of the 589 did bonded pair service start to be offered at less than 3000 feet allowing for internet 45/6 and very short distance internet 75/8. 

During this period 2WIRE was purchased be PACE and MOTOROLA was purchased by ARRIS. In 2015 both companies released new models from ATT the 599 upgrade of the 589 the PACE released the 5268. Both of these models were the first VDSL gateways to offer dual band 2.4Ghz b/g/n and 5Ghz n/ac along with (4) T100/T1000 ethernet ports.. LEDS include POWER, Broadband 1 and Broadband 2, Service, HPNA (coax connection indicator), voip 1 and voip 2, wireless connections, etc. 

In the early days ATT offered very limited fiber (BPON) with best speed of internet 18 matching the iNID speeds. The 3801 and 589 had RED ethernet ports to support connecting to the 210 ONT being used. The 599 and 5268 now offered it all... single or bonded pair, ADSL2+ or VDSL or direct fiber with dual band wireless as the newer ONTs such as the 240 were being placed offering internet 1000.  Again these were released in 3rd or 4th quarter of 2015 with ATT purchasing DirecTv summer of 2015 with requirement that ATT would provide at least 12.5_ million fiber addresses within 4 years of completing the DirecTv purchase (by late 2019) with ATT exceeding the goal (requirement) by 110% reaching over 14 million addresses. 

With more fiber being deployed, the function of installing ONTs were moved (by union contract negotiations from core CIM (InR) techs to UVERSE premise techs (PTs / WTs in southeast). It was  during this time in late 2017 that the BGW 210-700 was released with only (3) indicator lights... POWER, BROADBAND, PHONE (voip).  In essence as the ONT had 4 indicator lights the 210 only needed to show a connection was established. The wifi service of 2.4Ghz b/g/n and 5Ghz n/ac and ethernet ports of T100/T1000 are the same for all 3 models (599, 5268, 210) however it is clear to see the 599, 5268 with additional indicator LEDS is better suited to ADSL2+ / VDSL single or bonded service while the 210 with minimum indicators is intended for direct fiber service. 

All 3 models can be used interchangeable in all 3 UVERSE platforms of IP-CO / IP-RT (ADSL2+) VDSL FTTN and FTTP (FTTH). I personally prefer the 599, 5268 when GREEN port is the connection and using the 210 with RED ethernet fiber port is used.  However as the time passes, the models are getting older, but software updates continue to happen keeping the models similar.

Remember the history lesson above, the 589 released in late 2013 is still being carried on techs trucks and installed in 2021... mostly assigned to internet 10 or less where having only 2.4Ghz b/g/n is not an issue due to the lower speed tiers being used on. 

As a UVERSE tech in the midwest (Milwaukee market) my current inventory carried is (1) 589, (2) 5268, (3) 210 and (3) 320. The 320 is the newest gateway with build in ONT only available for NEW fiber installs, no separate ONT is used. Released in late 2020 the unit offers WIFI 6 (AX). 

Note that for the previous models mentioned, if move your service to a different address you are to take the current gateway with you. However with the 320 as it has the internal ONT which is assigned to that address, you leave the 320 behind if moving to a different address. Someone moving into that address then has working service as soon as the address is activated for the new account or moved account. 

We have had the 5268 for over 3 years now.  Consistently having dropouts over that timeframe.  I've called tech support previously, but on my last call they ran a "test" and said that they could see there was an issue with my modem.

So, they sent me a 210, because the "320 is not available in my area".  I noticed on the back that they covered the RED port and only left the GREEN broadband port open.  However, my 5268 is currently running through the RED (ont) port.  

Should I keep the 210 and run through its RED port or ask for another 5268?  OR should I demand that I get a 320?  

Thank you for any help!

If you have an external ONT then you need to plug the Ethernet cable from the ONT into the red port.

Sure, give the BGW210 a shot and see if that helps your dropout issue.  AT&T won't ship you a BGW320 at this time as they're in short supply and only given to new accounts.

I got my service about 5 years ago. I asked for an updated router since I had seen a 320 at my girlfriend's place recently, but was sent another 5268.

Is it worth replacing the original 5268 for BIOS or other updates presumably in the replacement one?

Thank you in advance.

AT&T routinely updates the firmware in place on active gateways, like the 5268AC, the BGW 210 and the BGW 320.  The BGW 320 is only going to new fiber installs, as there is a limited stock and it is the only Gateway to which Fiber can be run without an ONT, so you're not going to get a BGW 320 sent to you as a replacement, no matter what holy book the CSR swears on; he has no control of the actual gateway sent (the warehouse sends whatever it has on hand).

Recently, every so often I have had my internet service interrupted due to 'weak security'. The recommendation is for WPA2-PSK (AES), which is what I have. I contacted AT&T and they did a test and said they detected an equipment problem and they sent me a new router - the old one is a 5268AC and the new one is a BGW210. What I have read above is that these are basically the same, so is this really going to resolve the issue? I have yet to install it as my daughter is visiting and working from home, so I do not want to interrupt her ability to get her work done over the next couple days.

The BGW210 is getting firmware updates and the 5268AC is not, and the firmware for the two is a completely different codebase.  Unless you have a reason not to switch to the BGW210 (e.g. the coax connector is in use on the 5268AC), I'd recommend it.  Its Wi-Fi has always been slightly better than the 5268AC (though they're both 802.11ac devices, and both support WPA2).

Thanks. That is helpful, and reassuring.