Although I don't particularly agree that 24 is old.. being 29 myself the last thing Cyclone Duke says is absolutely spot on.

"Don't overthink this"

If you work too hard for the wrong one then you'll end up feeling stupid. Work out what you want first. If your after a more serious 'relationship' (there's a word us guys hate...) then I would suggest the older girl. However if all you're after is a bit of fun, then the younger girl might be up for it. However, this could all hit you smack in the face if it's not what they want.

Personally, I don't think you're ready for either since you don't know which one you want. What generally happens in situations like this is that whichever one you go for, you'll be thinking "what if".

I'd steer clear of both if I was you. Keep being friendly with them and all that but no more. Find someone else and go for them - there must be plenty around. Besides, as soon as you have one girl you'll instantly find out which of these other two are interested by which pursue you and which just walk away.