As someone who has had both the penile inversion and the colon graft, I don't really recommend either. They are both disappointing in their own ways. With the penile inversion, I had problems with depth and pain during intercourse. With the colon graft I had nearly two years ago, the depth problem is gone, but I still have pain during intercourse, plus an awful smell, I have to wear pads all the time for all the goo it spews out all day everyday, and it still bleeds frequently. Somoetimes the graft section kind of "convulses" and causes me discomfort at inconvenient times. I hear it tends to prolapse gradually over the years too. I'm really not looking forward to that.
Don't get me wrong. I had to get rid of that "thing." But I think I might have been just as happy with that surgery that just removes it entirely and leaves you with just a pee hole.
If I had to choose between the two, I'd recommend penile inversion. Maybe add a skin graft.