I didn't stay with Armada when I tried to watch it, and have not given Energon a try. However, I am currently going through Cybertron and really enjoy it. I know it is the third part in the Unicron series, but from reading descriptions of all three and watching it, it really can stand alone just fine.
Cybertron seems more "grown up" to me. The kids aren't half as annoying as the Armada trio, and the story is more interesting. There are mini-cons but they are not the main point of interest in the show by any means. I also find it more hard hitting and action-packed.
If you are not bothered by reading subtitles, watch Cybertron in Japanese original version, Galaxy Force. Thundercracker's weapon is "Thunder Hell" you just can't beat that. I also think that the music, etc. was toned down for US audiences. Galaxy Force has way more evil sounding organ music and fire in the background when the Destrons are shown.

Floats my boat.