Let me preface this first with, this is not a debate about which is better, just a question about what holds up better . Would buttercream or fondant do better in the heat and humidity? Would a specific recipe for either be best (meaning, is there a particular BC recipe or fondant recipe that holds up better than another)?

Thanks.

I would opt for fondant but not MMF as it wiill get melty and gummy-it's the marshmellows. I like MFF(Michele Foster's Fondant) even with white chocolate added it stands up to the heat.

shortening based bc holds up much better than butter based (try indydebis)
as to whether it holds up better than fondant i dont know. at any rate, you need something to attatch the fondant with!
also be sure to cover the basics with the client, the less time outside the better, in the sun is a no no - and if they ignore your advice, then it is not your responsibility.
xx

Thanks. Actually, this one is for my son's birthday party . I figured that fondant could sweat, and, as pointed out, has BC underneath anyway, causing it to slide off. But BC would tend to melt.
I will definitely check out indydebis shortening based BC and MFF (which I've been wanting to try anyway).