Obviously one you can get into quickly if you need to, small enough to fit into the space available, unqweildy enough that badguys can’t just walk off with it, and secure enough that breaking into it is a nonstarter.
That rules out plastic faced, glass fronted wooden uprights, and small tiny ones.
Beyond that, it boils down to money and personal preference.
Check the lock styles and pick one that you can open quickly.
>> Check the lock styles and pick one
...and if you CAN pick that one, move on to the next. :-)