Is a phone that supports the most network bands ideal if you are trying to get the best cellphone service?
It simply depends on the match between your phone modem (radio) capabilities and the band used by Telco(s) where you plan to use them. Other than this having capability to function in bands other than those your Telco(s) or carriers use neither adds nor detracts performance
It is a marketing decision to cater to a few bands which are reagion specific or broader (International models). Apple is more consolidated than splintered Android and that could be a reason for support to bigger range of bands
If you have a set of bands that your phone can support but are not supported by your carriers. Capability has no use
If your carrier(s) (as in roaming) support different bands and your phone supports them, it is good because your phone will work on all of them
Aside, you can see performance in the same mode widely varies within networks