the plastic terminals work fine for low power installations. they can and do melt and fail. i've had the larger banana connector terminals fail with under 500W RMS.
Bolts can work great and are easy to seal.
Parts Express sells terminals that are designed to be mounted through the sub box - giving you the best of both.
binding posts are cool, better than straight bolts IMO especially if you get ones with push terminal ends for the outside. but I've never had a problem with regular terminals and I usually use the push terminals that accept up to 8ga. wire