I like bullet format and team is more interesting for me.
By format, I meant more about the style of the tournament, such as Swiss/Elimination/Warzone(on Chesscube, called Arena on other sites).
I mentioned chess960 because as far as I know there is less chance of cheating.
That is no longer true, with lots of strong engines being able to play 960 now, there is little difference in cheat abilities in 960 and standard chess.