So far, I have experienced two differents senstations:
- with some girls, then main stimulation on the tip of your dick is when you enter her anus. The anal canal offers lots of friction and stimulation.
Once inside her, it's like to be in a very large empty room!! Only the shaft of your dick is getting direct stimulation.
You have to almost exit her to every stroke to get your dick head stimulated. Not all girls will like the feeling of you entering/exiting at each stroke.
Penetration will not be very deep though, unless you want to make it so. Difficult to go full speed when you need to control the exit move in order to stay within her just before total exit.
- with some other girls, once you have passed the anal canal, the tip of your dick will enter in contact with the rectum walls, like in a vagina. There the sensations are a total bliss, you can go ball deep and feel your partner all the way in and out. You can go full speed as well and keep the feeling.
The friction is also stronger than in a vagina, even if you put lots of lube. No lubricant can match the vagina moisture and softness.
I guess the second 'type" of anus is what makes guy crazy about anal.