I would take the higher number. Having the surrounds too low is a mistake. The reason is localization. You don't want to localize to to the surrounds. If you get them too low any seating near the surrounds, will localize and that will be a bad seat. You have to be careful if you have a tiered theater. You really do need to keep the surround's tweeters 5' above the floor at that location. I can assure you that a tiered theater can not be tied to the mains tweeter height, which ideally should be at 36".
Here is a picture.
The tweeter heights of the surrounds and rear backs, are 60" above the second tier. If they were lower then those second and third rows would localize to either the surrounds, rear backs, or both at times.
You really don't want any seat to localize to any speaker ever. If you do the sense of space and illusion is lost.
My advice is that if in doubt choose the higher level. It will be the safer bet.