No idea, but it was noticeably different - I'll have a check on the PTR later and do a proper comparison in case I'm talking bollocks, although I've seen mention of it in other posts too.
Edit:
Ok I just did a quick test on the PTR - 3 min runs just auto attacking, and did the tests twice both with the exact same result:
Sidewinders = 17 marking target procs in 3 mins
Arcane/Multi (with Trickshot) = 21 marking target procs in 3 mins
Pretty quick and dirty but at first glance there would appear to be a slight difference.