Lowry is better overall but IT is younger and is on a better contract.
Add to this that IT has made no secret of being excited to play in Boston and you have the ideal situation for a talented young team.
A year ago, I was still wondering whether IT will be good enough a starter if we make to become contenders again: his issue size could be a restriction both offensively and defensively at playoffs basketball.
His performance so far has convinced me that he could make it as long as we have elite athletes like Smart and Crowder giving a helping hand in the perimeter. This season's playoffs will be an interesting test.
EDIT: typo