In term of pure strength, Beamer is the best energy weapon, but its range is really low so I prefer Fragment which is a bit weaker but which has a big range and it's the best weapon to kill flying mobs like Valkyrie or Airhead.
If I pass over pure strength, I like Color Cannon, Laser Blaster and Revolution
Color cannon isn't a bad choice, but if you want more power and have a mind blaster and light upgrade kit laying around you can get that.
Soul Spark and Light Spark, instant kills non bosses
I never use those anyway since they consume most if not all your energy.
Anyways, I'm thinking of making a new AoA world (I'll use the same seed) because of another mod I have causing the entity count to spike to performance reducing numbers every time I go out to explore, even in peaceful, and the entity count doesn't go down unless I travel to other dimensions. Though I don't know how to use MCedit to transfer my base and my NBT Data over.
I thought I was the only one to find too much Savannas in my worlds...
In my current world, I had to travel thousands of blocks to find even an Extreme Hills biome with snow in it. Everything else was deserts, jungles, and swamps. Of course, I'm using BoP, so there are many more biomes in the world, however even then I could find barely any cold biomes.