Depends on the client. There's some that cum really quickly from oral. There are others that take ages to cum and so fucking them is a lot easier and more enjoyable for me.
Although I have a regular who enjoys giving me oral. Spends most of the booking making me cum before we fuck and he cums very, very quick. Also, have another one who just wants mutual oral, but wants me to be slow and stop sucking for ages.
But the one who takes ages to cum, I prefer to fuck. He's an amazing fuck I always walk away a few hours later thinking I should be paying him.
Someone mentioned smelly dicks. I tell them to go and wash or I walk.