For me double bass pedal is easier to play, maybe because I am not so "big" guy. You can have your feet closer one to another which makes it playing easier.
And also I've never been for 2 bass drums too much. You can see so many drummers who have 2 bass drums just to show his set, how big it looks on stage...and then he rarely uses the 2nd bass drum.
And at least I can play faster on double pedal
actually there is 0 difference if you have the gear set straight.
For example: playing with 2 bassdrums and using the bassdrums to hold your toms basically SUCKS, cause you can't get a 100% comfortable position on your hihat/left bassdrum pedal (assuming you're right handed). If you use a rack to hold the toms (like a Gibraltar or something), that can be handled.
With a double pedal you also just have to stick it under the hihat mout
Anyway, if you have 2 single pedals configured right, you can get the same performance you get with 1 double pedal.
Mostly big drummers use 2 bassdrums simply cause they can afford it and it looks cooler
actually if i WERE a rich ass i'd have a damn iron cobra
i had a crappy drumset, that i joined with my bassplayer's drumset (actually his dad's, but anyway)
so i play with 2 bassdrums. And my left pedal is so broken and so piece of shit that the only person who can actually play it is me