I don't get why some people like anal sex.
Lets look at the pro's, and cons.
Pro's: It feels tighter.
No risk of pregnancy.
Cons: Higher risk of STD's.
Makes your cock/strap on smell like shit.
Partner probably wont want to go down on you seeing as said cock/strap on smells like his/her shit.
Pros: Depending on the person, it may feel better.
If you're a gay man this is your own option at penetrating your partner besides oral.
Cons: Hurts more (usually).
Higher risk of STD's.
If you're a straight couple it seems to be more trouble than it's worth IMO.