The one that has her twitching uncontrollably and screaming YES loud enough to wake the neighbors. Even if you live next to a graveyard.
As to which actual position is best, that varies from couple to couple. Try them all, it only takes a year or so.
Obviously a younger person looking for a quick trick to curls some toes.
Oh gosh, try them all and have fun.
Butt once you can get past the pain.
There isn't one. Different strokes for different folks I guess.
My girlfriend loves being worked on with hands. She just loses control when I do it. But when it comes to actual intercourse shes not so much about the position as how I go about it. She wants to be kind of "taken". She wants me to throw her down, pull her butt up into the air [if thats the route I'm going for] and go at it hard while I hold her down on the bed and call her a whore and a slut [and no I'm not joking thats actually what she likes]. Just a note DO NOT try that with a girl as it's probably not gonna work out, thats just her personal preference, and if you come across one who wants that she's gonna let you know.
But the best route to go is just variety. Switch it up, do different things and have fun.