All depends on what you need
Dobson the growing all around D
Bouchard the one dimensional PP defenceman
If they continue the current growth projections, Dobson will be the more valuable of the two. But that’s hard to predict
Dobson is already playing 25+ minutes (NHL top-5) in all situations, is the #1PPQB, is currently PPG (32p in 30 games), and is a +17 on a team with a minus goal differential. He's been thriving as the #1D that has been carrying the defense with Pelech, Pulock, and one of Mayfield or Aho hurt at the same time. He's had multiple 30+ minute games and has been averaging 27+ in the last 8 games or so. He can benefit by adding another 10 pounds to his thin 200 pound frame, but Dobson is that do it all beast already.
Also, Dobson has shown quite a bit of offensive prowess at ES and as the PPQB that has essentially matched the reputed "offensively dynamic" Bouchard throughout their careers. So if Dobson is pretty much equal to Bouchard offensively and is superior defensively with pretty much no glaring flaws (other than still needing to add some weight) like Bouchard does, then wouldn't Dobson be the clear choice now?
Will Bouchard improve his defensive game that dramatically over his career? History shows that his type of d-man in the mold of Carlson, Mike Green, Shattenkirk rarely improve defensively and remain 1-dimensional offensive defenseman. These vague "let's wait and see" comments from Oiler fans make little sense to me, these 2 players are pretty much what their upside suggested at this time. At PPG+, they are both already NHL elite offensively. Are they going to match Orr numbers next? Is Dobson going to log 30+ minutes every night in the future?