Hmm, comparison time.
Buildcraft power: needs manual switching off, automatic switching off with gates, or machines that continually drain energy 'keeping warm', to prevent conduits from exploding.
Thermal Expansion power: a little tricky to make (electrum and liquid redstone), but has the benefit of only 1 type of conduit to keep track of. You'll want to disconnect machines that continually drain power, as there's no need to waste it and you'll be wanting to fill up energy cells with your energy surplus.
IC2 power: doesn't explode from energy buildup, but does vaporize stuff if you get the voltages wrong. Requires rubber. If not insulated enough can hurt players (that can still happen, right? I'm a bit out of date on this).
RP2 power: pretty straightforward really, but I haven't made any in quite a while so I can't comment on cost. I don't think anything can explode, right?
Factorization power: wiring based on lead, energy generation based on silver mirrors. Well I guess we can say it's unique but I don't think it's "for me".
Xycraft power: what little I've seen looks pretty awesome. Can cause serious damage to you if you walk into the beams. Also, isn't available to us common plebs.
Anyhow, at the moment my world is exclusively TE power. One of these days I'll find rubber (or my crossbreeding will succeed and I'll be able to grow it that way. I keep forgetting to check and finding my crops are weeds.)