I've done both incalls and outcalls over nearly 8 years in the game - Incalls have always been more popular, and as a result much more popular for repeat business.
But... I prefer outcalls as it means that when time's up I've got more control of when I get up and walk out, and also I'm not saddled with cleaning bedsheets, towels, the mess that guys always create in the bathroom etc...
Incalls much more popular though as from the punters view, all they have to do is turn up, do what needs doing, get dressed and go - easy.