okay please bear in mind i'm talking about this from a purely op fighting point, so both would be fully ppu supported and the like... i'm just basicly after a mass-opinion (not just from one certain clan) on which type of character is easier to play...
Anyway.. spies, take a little bit of effort to get a nice con setup but they also have the stealth tool which most "smart" spies use as soon as they feel in danger (below half hp or antibuffed while full hp), also they specialise in pistols which lock on the target almost as quickly as apu's and they also have no runspeed slowdown, then there's rifles which are (besides maybe creed) the only viable sniping weapons, the reticles closing almost as quickly as pistols and the runspeed nerf only taking effect on client side.
As for tanks, they take around 10-20% less damage and have a health pool around 100-200 hp more but they don't have any means of excape other than running, while they have a weapon out they're slower than most people so it's easier to hit them, their weapons also mostly have low clipsizes and their weapons take twice the time to get a lock on the target (which actually never gets as small as pistols/rifles get).. also adding in their inability to hack which does matter.. melee weapons aren't even worth mentioning since their 2.2 nerf.
PE's are possibly the best of both worlds, they get close to tank-like resistance, similar health pool sizes and they also get stealth to avoid fire/escape at the same time as using easy-to-aim weapons.
Just to emphasise a little on how usefull stealth is in op fighting, in my clan we generally attack the same target's and call the target's on voice comms.. and mostly we take down apu's first followed by tanks due to their lack of stealth.. then when it comes down to spies and pe's we hold off attacking them until they're antibuffed so we have as much chance as possible to hit them before they stealth (if we start shooting them before the antibuff they'll have worked out they're the target and stealthed).. basicly stealth instantly stops you being the designated target... how can tanks do this? run out the op? (what i do - sometimes works), zone into the underground (if availible), or drop dead....
please try not to just flame saying the usual crap like ZOMG ALL TANKZ DO IZ CLIPWHORE cause every character does that, it's just harder to notice when spies do it cause when they're taking cover hiding behind something you can't see them cause they're in a nice little stealth bubble (although i often set that cloud on fire so i see they clip as much as anyone else that's "hiding")