I have NEVER, NEVER, NEVER liked shoulder holsters...but like Chevy vs Ford, and Glock vs XD...that is personal preference, once one understands how a shoulder holster is supposed to be worn and used. The low slung TV and movie look is useless as hen poop on a pump handle, it should fit very much like a vest so there is no flop and your gun is ALWAYS in the same position. In my opinion, if you LIKE a houlder rig...then it works for riding because the gn is protected from road rash in the event of a crash.
Likewise, crossdraw in a good holster (no nylon crap) preferably with a retention device of some kind, which I normally eschew in favor of a properly molded and fitted holster works well, as it is protected from a snatch, or even from some "do gooder" seeing your piece and calling LE about a "biker with a gun". Use caution here though, and avoid ANY type of clip-on but rather go with a snap-on IWB with at least two snap closures, and preferably one that wraps all the way around your belt. I'd hate to see you go down, survive the crash, only to watch your pistol slide along the pavement for another 200 feet or so.
When I used to ride, I carried in a leather vest that I modified to carry a holster and a pair of spare mags. You couldn't see the pistol, even if you looked inside the vest, as one had to go through a velcro closure to get to it. it was fast, and secure.