I honestly think both teams have gotten better if they play their cards right.
Assuming Cleveland starts Thomas (PG), Crowder (SG), Lebron (SF), Love (PF), Thompson (C) I think that the addition of Crowder makes that a stronger all-round lineup then they had last season. This allows them to bring Rose off the bench as an offensive sparkplug, which also means they can restrict his minutes and reduce chances of him getting injured again - I think this is the best possible scenario for Cleveland.
If Cleveland starts Thomas and Rose (bringing Crowder off the bench) then I think that makes them worse, because Crowder is IMHO a better overall player then Rose and a better for for the team given his size and two-way skill set. A backcourt of Thomas/Rose would, IMHO, be a defensive disaster - especially with Lebron (who plays D when he feels like it) and Love out there as well. I cant imagine they would be silly enough to do that.
Wether Boston gets better or worse will depend very heavily on their youth movement at this stage. One of Brown / Tatum / Smart is eventually going to be expected to start in Crowder's place, and those will be big shoes to fill for three guys who all (IMHO) have a lot to prove:
* Can Brown show significant improvement over last year and prove he is worthy of starting?
* Can Smart finally provide some passable outside shooting to compliment his bulldog D?
* Can Tatum score against the big boys as well as he did in college and summer league?
As one of those guys moves into the starting five, then that also opens up extra bench minutes the other two guys plus Rozier.
Boston has a lot of dark horses in this race - a lot of young prospects who could just as easily break out or doing nothing at all.