The Stormy Mondays will cover the blues and lighter end of the rock era, unless the guitarist was using a Strat, and then you can wind down the volume and get a really nice clean tone with Stormy Mondays. If you think of early Fleetwood Mac through Wishbone Ash, then you will be in the tone field of SM's. I can also get the Clapton Cream Crossroads tone from my 335 (SM unpotted AII's).
The mule is a fatter sound, with more low mids and bottom, think more of the later Gary Moore sounds or Stan Webb (Chicken Shack), Paul Kossoff (Free) or even some Zeppelin. They still clean up quite nicely, but without the shimmer of the Stormy Mondays.