Well, good question...  At first blush, I'd go with a vertical.  Depends
though what you mean by maximum coverage?

Do you mean covering a good area or do you mean getting maximum range as in
DX?

For the latter, definitely a vertical, so long as you can put in a good
system of radials.  I know you can get some performance with a system with
ground rods, but I don't think it is as effective as laying down at least
fifty radials of varying lengths.

If, on the other hand, you mean maximum coverage including closer-in, and
covering most of the bands, nothing beats a 130-foot dipole or inverted vee
fed with open wire and a tuner.  Being a wire antenna, it is pretty
inconspicuous.

Steve, K8SP