In terms of this year's production, he's the best UFA out there. Largely because of that, Dallas will fight tooth and nail to resign him. Chandler will probably give the edge to Dallas as well, given that he's won a championship and seems to have good rapport with teammates.
I'm probably in the minority here, but I actually like Dalembert more than Chandler--Dalembert is much more the iron man (many people forget that Chandler has had injury spats in the past, and as he gets to his 30s his athleticism-based game might suffer more) and IMO more defensively consistent--his impact on the court has been up there in seasons past (it's just that Philly, as with the case of Iguodala, has a bad habit of severely underrating their defensively capable players). Because of that, I'm not sure if Chandler can match this level of production in subsequent years--obviously, a minor slip is nothing--but Dallas has to be a bit skeptical after signing Brendan Haywood to that fat contract a year back. Things that make you go hmmm.
As for JJ Barea, this season he seriously improved by leaps and bounds--a lot of people also forget that he also had a very good regular season. And then he blew up in the playoffs. The guy's absolutely feisty and a fighter, one of the toughest sub-6 foot guards in the league, made even moreso given the lack of uppity athleticism. But he's both quick and shifty quick, uber confident, decisively makes his moves, has the ballhandling skills to get to his interior spots, and the court vision and the dare to make one-hand push passes outside or to cutters. He can take several defenders on, even those that are probably more than 2x athletic than he is. And of course, his defense seriously improved from last year, he draws charges, and is an underrated shooter (those timely threes in the playoffs in particular). In a way, that's sort of poor man's Steve Nash material. He'll definitely be a fat contract, although once again I think the Mavs might hesitate (they have four talented guards of PG size, so the decision might come down to sack Beaubois if Barea comes back).
Again, I'm probably in the minority here, but do we really need Barea when we have a bit of a facsimile in him in...Udrih? And I actually thought Udrih produced one of his better seasons with us this year, and his output in terms of impact was a bit similar to Barea's. Udrih's probably less of a PG, but he has the same daring ability to land in the mid-range (where he's absolutely money) and also has the whirling dervish ability to spin his way to the basket. The difference IMO isn't all that great, and if we're stuck with Udrih we should optimize around him with an athletic speedster type (some say Brandon Knight/Kemba Walker) or if we trade him just get a whole new prototype. So I don't think Barea would be feasible whatever we do.