Two speed pumps are in spas for two main purposes:
1) They are used for filtering on spas that don't utilize a circ pump for that purpose,
2) They are used to create water flow for heating for spas that don't utilize a circ pump for that purpose,
Since the spa you are considering has a circ pump (my preference in fact) there is no requirement for a 2-speed pump. Sure some sales people will say the low speed gives a soft tissue massage but I think that's sales mumbo jumbo and if a spa company tomorrow decided to switch to a circ pump they'd proably drop to a single speed pump in a heartbeat. Single speed pumps are even more reliable long term than 2 speed pumps but not to the degree that the 2-speed pumps are a problem, just a side note (and the single speed pumps are cheaper when replacing).
I guess what I'm saying is I wouldn't give it a thought either way when deciding which spa to purchase.