It depends what you want.. red is very diff than blue.
I rolled a sham, one of my favorite classes.. but on red but didnt enjoy it as much. its really more of a buff bot/support class, you do like 90% more buffing on red. I wont speak to its power in pvp, I think in the right hands can be very powerful, but I wasnt good at it at all!
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Also soloing stuff the way you do on blue is a lot more difficult, you tend to want more pals to come with for pvp that
will show up.
Rogues are always wanted, and very fulfilling class! If it turns out you like pvp, youll love that you rolled a rogue.
All melee's are really fun and great in pvp and only get stronger and stronger the more you play them.
Druids are also fun, and can do a lot with the playstyle on red, on average there are way more alpha druids on red than there are on blue, save a select few!
Enchanters are terrible on red (sorry readers!). Not the class, but the players. So good ones are very welcome in guilds and groups! Really good if you want to do solo camps, cus you can sneak around better than a shaman.
If you really enjoy the playstyle of a shaman, or enchanter and want to do more pve stuff, a monk is really great, but expensive to gear just like blue!
Wizards are popular for lower level pvp and there are a lot more on red than blue, and good!
Bards are bards, and very welcome too same as blue.
I hope that helps!