Favorite year: 99-00 or 01-04?

The newest car you can afford is always the right answer, but either way the '01-'04 would get my vote. The Romeo engine seems to get all the attention with the aftermarket since that what most Ford 2V's were running. The Windsors only got a short 2-year run in the Mustang and was otherwise designated to Truck duty.

Mechanically, one is really no better than the other so at this point you're pretty much addressing age and wear and tear.