WhatsApp Babe vs. Facebook Babe

WHO'D YOU RATHER?

2/26/2014 12:10 AM PST BY TMZ STAFF
0225_whatsapp_facebook_girls_rather_launchHere's the insanely rich WhatsApp co-founder Jan Koum posing with his gorgeous girlfriend in Spain earlier this week (left)... and the Facebook baller who purchased the app from him -- Mark Zuckerberg with his beautiful wife (right).

The billion dollar question is...