Loaded question,
But IMO, I'd go the zetec for a few reasons,
1 its been done plenty so heaps of info is available
2 Type 9 bolts up
3 plenty of conversion parts and options
4 Reliability and driveability for me Zetec wins
5 You can make it look just as right as a pinto would look in the engine bay AKA BDA replica
6 Cheap aftermarket parts ex USA
7 Lighter than pinto
8 I wasted good money on a big hp pinto build but have made similar hp and better reliability from my Zetec. Just personal experience is all.
9 its a bit of a challenge
Again its a loaded question that will depend on alot of factors, but ultimately I'd go zetec.