Just to clarify, the 315 does have just one pump w/2 speeds but its a 1.5hp continuous, 2.0hp brake compared to the 365 which is 2.5hp cont. and 4.2hp brake, not a very fair comparison. Not to discount the pump in the 315, cuz its probably just right for that tub size. Just saying, you cant sit in a 365 and think it will feel the same.
Any dealer should be able to fill up a tub on his floor for you to wet test. If they wont do this, then I'd be leary of doing business with them.