white paint is the way to go, hands down!

with foil, you have the pain of installing it (you'll never get it completely flat) and
any wrinkles are potential hot spots.

foil is also a much bigger pain to clean, you will tear it!

also, white paint is nearly as reflective as Mylar (which is way better than foil),
like 90% for paint and 95% for Mylar, so the trade off is 5% reflectivity in exchange
for ease of use and clean up, and durability as well.

once you paint it, you can forget it.

oh yeah, btw, if you go to Lowes or Home Depot and go to the roofing department,
you can get elastomeric paint, it's flat white and rubberized, it's made to seal
roofs, so it's waterproof, plus, it's resistant to mold and mildew, i guess because
of the rubber. and it's cheap at like $15.00 a gallon!

here's a pic of my new mother cab for an example.