Get a hard cup. You are protecting your nuts from something going 300 feet per second. I've had bruises big enough that I'd be in the emergency room if they were between my legs. Now on to cup buying. Bike has a super nice cup, rubber on the sides, but the strap is crappy. Get the XXL if you get it because the strap is to small. If you are looking for a soft/foam and can't find it anywhere this place will have it:
People are crazy to not play with some kind of protection.