It really doesn't matter what you join, as long that once your in a faction, you look for a good clan.
If you want to talk advantages, than it's either Raven or SVER, because Valor is harder to play for.
SVER has more power, Raven has more accuracy, that's the gist of it. Valor requires more teamwork. So while you tend to find better players on Valor, there's just fewer of them because it's that much harder to play in Valor and succeed due to they never have a technical advantage over the other team, and when defending for Valor, it's easiest for enemies to flank them. SVER and Ravan maps are more difficult to flank.
---------- Post added at 08:21 AM ---------- Previous post was at 08:17 AM ----------
Oh, and FYI...
When you get into this game, please please please...
Do not join the main battle maps right away. Do the training first, get your free skill point, and then join the "Skirmish" battle called Suppression so you get used to the game in general. Lastly, make sure the first skills you get are the med kit, and resussitation....you get several exp healing a person (1-2 points per second of healing...which depends on how hurt the guy is you're healing) and 10 points per revival of any player. This 1) gives you quick experience points to help you develop your skills faster and 2) teaches you how to support the better players first, before trying to go out on the front line of things. This isn't COD, it takes much more time invested to actually become a decent player. It might be frustrating at first, but stick with it.
If you want to join up with me so I can teach you the ropes, I'm currently doing SVER. Join it, add DarksunDaFirst, and I'll show you some things.