I like 120 because it's cheaper to buy two rolls of 120 than it is to buy 1 roll of 220 in most cases. If money wasn't an option I would shoot 220 as you have to reload have as often.
If you're developing yourself 220 is longer which means more time rolling onto the spool.
Not much difference really, I think it comes down to whether you want to spend more money and reload less often or vice versa. Also some films are not available in 220.
Anyone else want to jump in here?