Beyond the updates, theres a couple reasons to get the T-Mobile version over the unlocked.
The unlocked version handles band 12 very oddly. I have a spot in my house that doesnt get great band 4 so when my T-Mobile version hits -110db it will swap to band 12 and once its on band 12 it will stay there with a signal of -89db. On the unlocked version it was flipping back and forth repeatedly and not switching to band 12 until -120db sometimes. My signal was bouncing around to the point that I could watch it happen.
The little HD voice icon in calls doesnt show up on the unlocked version but I dont know if that means it isnt fully utilizing HD Voice or not.
At first I thought battery was roughly the same between the 2 versions but what Im seeing today compared to yesterday is very different. Yesterday at this point with the same usage I was at 70%. Today Im at 82%. I think that directly related to the radio tweaks in the T-Mobile variant. Also, last night I lost 2% while sleeping for 7 hours. On the unlocked version I lost 12% while sleeping almost 8 hours. Again, I contribute that to the signal bouncing around.