Well.. I know that Halo for OGXbox had servers runing for more than 2 decades and there's still a lot of servers kept by fans, however, I wouldn't use network services aa reasn to choose device from that era. I personally, hunt for both of them in relativelly low price, but I'm a hoarder. In fact, if I would want to use online services I would personally look between XOne/PS4, du to fact, that community will live longer and they still can get a lot of benefits from owning PSN/XboxLive subscription, and first releases are in similar prices (especially in my area), as last X360/PS3.. You know, only small percent games is in GamePass that was desifned for 360, same as fac that they currently give games for PS4 & 5 in PSN...

So if OP has to choose, anybody actually, I would suggest different factors, like listo of single titles you're interested in, or accessability of games in your area..