I like my PS5100. I have to have a bit of a light touch with the 18" 3/8 bar that is currently on it, though. It might benefit from getting a few extra bananas stuffed in, or since I am rebuilding a couple MS261's and 550 XP's right now, I could build up one of them.
I got one of the MS261's running, and tuned it using a 16" .325 bar this weekend. It seems to like that combination, but doesn't seem to quite have the torque of the Dolmar. I didn't run it directly side by side with the 5100, though, so that may not be a completely fair comparison. It did feel a little more nimble in my hand, but weight wise, they are pretty close.
I almost have one of the 550XP's together again. Christmas has been keeping me busy, so hopefully next week I can get it together, and maybe run all 3 side x side for a more fair comparison.
But, if I do that, would I then want to get some work done to the weakest feeling saw to get it up on par with the other two, or take the strongest one and make it even stronger?