yes they load slower and need to sync, but if we are looking at the small details between trophies and achievements, I think trophies are better in all other ways.
There is bronze, silver, gold which is much richer than achievements. You gain an overall score which levels you up much like an rpg. this is yet another great addition.
I know the OP was aware of this, but all you have to do is START with trophies. Once you are earning them, competing with your friends to earn them, comparing trophies... the "achievements" really become a thing of the past. (which they are)
There is much room for structural improvement to the PSN, (even though its really close to XBL as is), but that is a different argument. That does not change the fact that at their fundamental core concept; trophies, and achievements are extremely comparable, but trophies have added a richer level of integration to the formula
They are almost a direct rip off, but they are better in all of the ways that matter.
It is written.