I like suits that look functional and where you can't immediately tell the team's theme by looking at them.
I'm big on the core five Boukenger's suits, because it's harder to tell looking at them that they're superheroes. They're not campy or flashy, they look practical and utilitarian for a team of explorers. Unfortunately BoukenSilver's has those awful beacons on it.
After them, the Goseigers. I love the animal designs on the sides of the helmet instead of holding the face in their jaws like most animal helmets. Their suit design is simple, aesthetically pleasing, and you can't tell at all that they're angels.