I'm not sure it's as simple as saying Bonino was a better playmaker and had better vision. It's absolutely true, of course, but I think you need to factor other things into a player: Like skating.
As smart as Bonino was, he was never a guy that could beat a lot of players to pucks, or out skate them and create room. He just didn't have that ability. Nor did he really have the strength and power in his game to skate through players, like Maroon does(another player with skating issues). He didn't just need to use his intelligence to be a good player, he had to use it to be an NHL player period. I think that places limits on what kind of player he can become, and how much better he can be.
I think his play on the PP helps reinforce this point. We all seemed to love him there, and is it really a coincidence? The ice is cut in more than half, and it is less about mobility by skating and more about moving the puck in passing plays. He wasn't asked to carry the puck into the zone, and it seemed like his responsibility was hounding the puck and looking for soft areas in the coverage.
At any rate, I wish him the best in Vancouver. I've been rooting for the guy since we picked him up from San Jose, and he was in BU. I hope he can find his way back here, at some point. It sucks to see him go, but adding Kesler should absolutely make us a better team. Kesler is a three zone player, who brings us a strong #2 center that we've lacked for a long time. Even if the offensive numbers are similar(and I'm not convinced they will be, because I think we can give Kesler more help than he had in Vancouver), I think Kesler will give us a much better overall game than Bonino is capable of. Losing Sbisa is, thankfully, little more than a footnote right now(as are the draft picks), because he just didn't have a place here. He's kind the complete opposite of Bonino. Lots of talent, but he just doesn't seem to have the smarts to utilize them properly.