M105, like GeorgiaHybrid mentioned, is a compound and therefor is stronger than SIP which is a polish. That said, M105 is also an incredibly unique product as it transcends traditional qualifications of compounds in that it finishes out as well as most medium polishes. In fact, I would bet in many cases you will find M105 to finish out almost the same (better or worse, given the individual case) than SIP.
That said, it can be a huge time saver for deep swirls or RIDS, but should also be avoided for incredibly soft paint when a more mild product like SIP could get the job done.