You would not be any better off with Ubuntu
The reason that OEMs are starting to itch about an alternative to Android is because Google tightens the screws on what they do with Android a little more with each release. This alternative would also add potential sources of revenue they could get if for example they made a deal with Microsoft to put Bing stuff on their phones instead of Google's stuff.
So you'd see more provider customization on Ubuntu phones, not less. Yeah, maybe they leave you root (unless the OEM takes it away) so if you know what you are doing you can remove the bloatware and update it yourself, but that's a solution for the 1%. For the typical user the update situation with an Ubuntu phone would be no better than it is now with an Android phone.
Biting the hand that feeds IT
