Jim may be correct, I haven't crashed (yet) while wearing a shoulder rig. I'll let you know after it happens!
I've worn the following three handgun/shoulder rig options, with the following results:
* Bianchi shoulder rig for S&W Mdl 19 2.5" bbl snubbie, elastic harness, nothing on offside;
* Galco Miami Classic rig for Para P-12 .45 ACP (wide 'jackass leather' shoulder straps) in tan, 2 vertical mags on offside;
* Galco Miami Classic II rig for Colt Cmndr .45 ACP (narrow leather shoulder straps) in black, 2 horizontal mags on offside;
The Bianchi with the Mdl 19 was extremely comfortable and rode well during a 5 day trip (2 days down, 1 day there, 2 days back), in June in Georgia. Drawbacks were that it rained hard and frequently, the holster got wet and stayed that way until I could get a hotel with a hair dryer and dry it out. Since my Mdl 19 is blued, allowing it to reside in a damp leather holster for several days did not seem prudent. (Nylon would have dried far more quickly.)
The Para-12 in the Galco Classic did not work well at all. I was wearing a Joe Rocket Mesh jacket in August on a 7 day ride. I didn't realize it (at first) but the wide shoulder straps were visible at my neck line; the mesh jacket features a relatively open neckline. Wide harness straps are not advisable. The doublestack mags and pistol on both sides of my chest felt bulky and were quite noticeable, (at least to me,) and the pistol/rig combination was simply not real comfortable. Additionally, it was August and you couldn't remove your jacket. Temps hit around mid 90s to low 100s coming across Illinois and Ohio that summer. I'd do things differently if I were doing it again.
The Colt in the Galco Classic II works great. Different cut to the straps and rig, single stack mags, different configuration, whatever, its totally comfortable and its what I wear now during Fall/Winter/Spring. It won't fit under a leather vest without showing, and for the hottest days of summer I'll no doubt go to a Kahr inside my riding vest, which (clearly) won't show when I need to remove the vest.
I'd prefer the shoulder rig style with no mags on the off side, (e.g. the S&W Mdl 19), except for the simple fact that if I ever were to get into a gunfight I'd rather be holding the Colt .45 than the Mdl 19 .357. Just a matter of personal training, ability to reload, etc. - 9 rounds of .45 with a quicker reload beats 6 rounds of .357 with a much slower reload (for me at least). Sort of a personal tactical conclusion.
Your mileage may vary.
(Whichever way you decide, black nylon might be a better choice of material than leather: even if it doesn't rain, you'll discover the holster damp from sweat from time to time.) And in the summer you won't be able to remove your jacket! Make sure you have a Plan B if you ever intend to wear either a mesh jacket or a vest... (On the other hand, with a shoulder rig versus a belt carry option, you can use the restroom while touring without screwing around holding the gun or setting it down somewhere inside the stall...)
Best with your decision, and if at all possible, try before you buy. Shoulder rigs are expensive, and the first one you try on may not necessarily be your best option.
Doc