its UPS.. when you order ground it usually takes 5 business days, 4 if your lucky.
so the 2 weekend days dont count.. but its insured and trackable.. which USPS is not.
USPS priority is faster, but not insured and not trackable.. and more expensive than ground.
from a quality and assuredness standpoint UPS is better. for speed USPS, though only as compared to ground...
beleive that you can request USPS but you may have to call in or email your order.
UPS is better.. just may be a little slower.. though that depends on where you are and what hubs are near you.. it can be a lot faster even with ground.. from AZ to CA its that way..