As for which is best – it’s less a case of personal preference, more a case of which type of electric oven you choose. Recirculating venting vs. external venting is more about the type of microwave in question, as opposed to anything to do with its performance or desirability.
In any case, convertible microwaves and convection microwaves are available, which come with the option of using a recirculation kit to switch from one venting option to the other.