A lot of the problems with the earlier link were probably due to hosting issues (the lag in the training was obvious).
This newer video looks a lot better, and pretty amazing for a 360 title honestly :
http://www.twitch.tv/cityflex/b/517930441
Remember, twitch video quality is basically garbage, it will look WAY better direct to a good display from a 360.
For example, look at this :
https://www.youtube.com/watch?v=-_ZOq8t9zEc
I've played a decent bit of TF on the XB1, and it looks MUCH better without the hella compression online.
Still, it's an engine from 2004, so we can't pick on it too much for having last-gen graphics. The XB1 version really isn't that much different from the 360 version, and the PC version is the same deal with higher resolution/AA (as long as the PC is fast enough of course).
Gameplay > graphics. For those that like it/love it, we have a new platform that looks totally worthy of it.
As for them holding it back, yeah it's not really crazy different. If Titanfall was the only reason for someone to want an XB1, and they already had a 360, then the 360 version is probably good enough honestly. But of course the XB1 has a load more games besides Titanfall both now and on the way, so investing in an XB1 isn't a bad option for those that want the exclusives.