Personally Lava is the simple but effective solution, with EE3 in place you can easily get to the nether before even getting diamonds. which is a plus as the nether is no longer end game. I do enjoy the options but after finding out the hassles of reactors and the slow gain I quickly upgraded to advanced solars for my EU production but found that it also crippled me because I was dependent on that. Lava is def a forgettable power source, moreso if you have a lava mystcraft age, that only needs a rare maintanence every so often but if you're like me I always have spots mapped out and ready to go before hand so it's as easy as transfering equipment from one spot to another. MJ is the standard, I'm happy sticking to it.