Actually for me it's about the feeling
If she stops and finishes with her hand it's a total different feeling that's not as good as her mouth.
If she let's me come in her mouth and she is going to spit typical she will stop suckling as I cum.
If she is going to swallow, as I cum I can feel the girls much suck down the cum and it just makes for a much better orgasm.
That being said I won't expect the girl to swallow. I would much prefer her to enjoy it as much as she can and she knows I always return the favor with interest.
Advanced Wordsmith