I've got a level 28 paladin and I've not had any issue with getting groups. I think tanks are so rare that most groups are happy to get what they can, and if you're decent you get tossed on everyone's friends list and get invites as soon as you log on. Only issue I really have with my paladin is having to use Flash of Light for agro at this point and that kind of restricts my ability to move during fights if we get an add or someone pulls agro on a 2+ pull.
Big thing with SKs is better race options and getting Disease Cloud at 9. FD, invis, CoS, lifetaps, snare, etc are all pretty tits but on Pal you get hp buffs, root, heals, paci and LoH. I think in smaller groups, paladin is a little more versatile but it really comes down to what you're doing and what levels.