Mine is a built in. Takes about 15 mins to empty both the black and grey tanks if they're both pretty full. It also depends on the distance the sewer is away from the coach. I've pumped about 150' from the coach and it seemed to take a little longer but I was only emptying the grey tank.
PROS: Easy to dump. No mess, You can eat a sandwich while dumping..:W...easy to store. It's a MUST for any coach we buy. I've had two.
CONS: Takes longer to dump. Annual maintenance, for me anyway, is to disassemble the pump and clean out any hair or debris left on the blades. Impeller needs to be replaced about every five years. $60 item, 15 mins work.
Hope this helps...Dennis