They are both similiar classes with slight differences. Check out their skill lists and see what catches your interest. Arakasi is correct, you can't be an evil swashbuckler or a good brigand.
Keep in mind that eventually you'll most likely be grouping with members of the other faction, so even though there may be a lot of SKs in Freeport, it's not so bad once you start mixing in with all of the Pallies from Qeynos (for example).
Is there any significant strategic difference between the two? Would prefer not to get to level 20 and discover took wrong path.
And if anyone has an answer to that what about difference between illusionist and coercer.
Or is it going to be like EQ1 where early choices didnt really limit you much.
1. Swashies are dps; Brigands are debuffers. I just betrayed a dark elf to Kelethin... it was quick and borning but it didn't want to make me stick needles in my eyes because of the repetitive required citizen tasks.
2. Illusionists use a spell to cast their pet which looks just like themselves; Coercers charm their pets from the mobs around them and the pet can eventually become un-charmed.
Very happy with the brigand, I can't do as much dps as a swashy, but I do a good amount and when I'm in a group, by help makes sure that sucker goes down fast. I've played Assassin and Brigand both to 50+ and I prefer the brig because of his greater utility. The assassin is also not as easy to solo because of the more limited ways to immobilize the target for positional attacks. As a brigand I have 3-4 ways to face a foes back and for normal mobs they usually never even get to attack back.