Mobile is so hot, because the conversion rate is much higher versus desktop, One major reason for this is; the payment flow. the payment flow is much (user) friendly with mobile.
For mobile you have mobile content billing (MCB) the advantage is that you don't need to give any details or even a credit card isn't needed. Just one click at the confirm button will do the job! Also premium SMS billing is hot nowadays on mobile.
The PPS would be in general lower, because the money that is spend on mobile is lower. Usually are these subscriptions rebilled every week. But if you are not satisfied with the PPS commission you should go for revenue share. In general the revenue will be higher on longterm.
__________________
|