Phoenix can't win in LA (their bench only plays super well at home), so it's a moot point, but I'd say Phoenix.
Look, teams like Phoenix gave us trouble in the regular season. But Boston is exactly the kind of team that Phoenix doesn't want to face. Our best defenders are at their positions of strength (PG and PF) and we're all around a great defensive team. If the Magic can't decimate us from 3, I don't expect the Suns to do so.
Nash is having trouble with Derek Fisher right now...just wait till Rondo gets a crack at him. Not to mention, STAT and Frye will be so easy for Rondo to score on inside, it would be marvelous to behold.
The Suns would be very difficult to defeat at home, but I think we'd steal at least one game there, and I'm confident we'd defend our home court (as long as we don't go up 3-0

).
The Lakers are much scarier in my opinion. Kobe and Gasol are so much better than Nash and STAT. The Suns are very imposing when they are hitting tons of 3's, but they don't have the full package on both ends of the floor the way the Lakers do.