You don't get to choose.

You get behind her and rub your cock along her ass crack, while squeezing her asscheeks together and smearing them with precum oozing from your painfully erect dick. Tina moans and wriggles her ass which arouses you even more. You grab your cock and thrust it between her thighs rubbing it along her pussy slit, making Tina shudder when your mushroom touches her sensitive clit.

You decided to go for the safe choice ... fuck her pussy and after that, if she'll agree and if you still could, you can go for her backdoor.

You rub your dick between her pussy lips some more and get it coated with her juices making sure it will slide in easily. You grab her hips and align your cock head to her wet entrance preparing to thrust in.

This would be the first time you cheated on your wife, Audrey, and you are quite excited. The excitement is even bigger as you are going to cheat on her with one of your friends and because the risk of being caught is high.

As you prepare to shove your cock in Tina's pussy you hear the front door of the house opening and someone calling your name. Damn it! It is Audrey.

Only now you realize you've been missing for quite some time. Acting fast you tuck your boner in your pants and zip them fast. You turn the corner trying to prevent Audrey from seeing Tina in her disheveled state. You walk to your wife trying to look drunk so she wouldn't start questioning why it took you so long to take a leak.