They are almost the same thing. They perform the same function but because they are physical invisible they are even less likely to be used by an average computer user.
I have some anecdotal evidence on the contrary. My wife is a very casual computer user, but uses two-finger scroll all the time. My sister-in-law is very similar - not a computer person, but has an Apple laptop and uses two-finger scroll. Also, Apple mice support scrolling[1], and almost any third-party mouse you buy will have a scroll button as well. Scrolling with a mouse or trackpad seems like an integral part of user interaction.
[1] http://store.apple.com/us/product/MB829LL/A?fnode=MTY1NDA1Mg...