My rule of thumb has been “the less moving parts, the better”. Whenever I purchase anything for my properties, I go for simplicity. Complicated electrical or mechanical equipment has the propensity to break down, causing hassle and expense for the host, and also fodder for the guest.
On the other hand, it’s wise to at least keep up with what the expectations are in your area. If most of the other short term rentals have hot tubs, and they are highly advertised and known to be used often by guests in your area, I probably wouldn’t want to be the only home without one.
I’m pondering a similar question about having a barbecue grill. Our complex has a few public grills, but about half of the units also have a private grill on the lanai. So far, safety concerns and the extra work our housecleaner would have to keep it clean has kept me from getting one.