Tauren is easily the best PvP race. War Stomp doesn't trigger the GCD so that's a guaranteed 2 sec window to cast in. For an enhance Shaman that's a guaranteed LHW (or GW to gtfo). For an Ele Shaman that's LHW/Lightning Bolt/Chain Lightning. Also Taurens get +5% health which is good against everything. Orcs by contrast have Bloodfury (which is a marginal damage boost in exchange for ruining your self-heals, so it's pretty bad) and Hardiness (but the Shaman PvP trinket plus Living Action Potion will already break 2 stuns instead of depending on a proc). Don't get me wrong, Orc is a good race thanks to Hardiness, but Tauren is so much better for PvP (plus your PvP trinket works on stuns) that it's the best choice.
If you're going Enhance Shaman for the PvP I would also recommend going Engineering. Goblin Rocket Boots provide a much-needed 70% sprint on a 5min cd plus you get extra slows from Discombobulator Rays in addition to the usual engineering utility and Gnomish Net-o-Matic to root enemies while you beat them senseless.
For PvE, Enhance is the best spec for leveling up but the worst spec for raiding. If you carry a Nightfall guilds will usually make space for 1 Enhance shaman but otherwise you have to raid as resto. I guess you could try a 0/11/31+9 Resto Shaman which is far from optimal as an Enhance build but it still has PvP viability in that you can play healer, beat face with a 2H windfury, and perform NS combos. Maybe you could get away with something like
this. Otherwise get used to farming up gold for weekly respecs.