For most people, there will be little difference or benefit between 7.1 and 7.2.
For me, the .2 is pretty important. I intend to run stereo subs. Splitting the .1 to two subs is not the same as running stereo. In my experience, the difference is mostly noticeable on orchestral, live jazz and acoustic music recordings. It's a nit-picky, hair-splitting preference to be sure, as it is a debatable point concerning sound quality, taking into account that bass is generally not localized from the source.