@superdavide I was wondering the same after buying a new pair of 3 Deco X50's to go alongside the 3 I bought last year.

I called customer support and they could tell me the following:

* All versions of the Deco X50 do receive updates (it's not like with other devices, where latest = greatest and old versions are less supported)
* In fact, V1 is the first to receive new features. Currently those features are added to V1.2, V2, V3 later. If you want the latest and greatest you should look for a V1

* Signal strength should not matter - it seems these units just have different hardware as you said. I'm not sure if the 3 antennas make for a better signal, but according to support the strength is mostly limited by legal limits in the EU so it makes no difference.

* For some other Deco devices, like the M5, they have a unified firmware version for the different hardware versions, so they are always in sync. This is not the case for the Deco X50. I guess we might see it in the future

* They could not really tell me what else the difference was between the versions, hardware-wise.

Based on this, I think there is no "correct" version to buy, they are all fine - but if you absolutely want/need the newest firmware a.s.a.p., you should buy a V1