The English Alpinist wrote:it looks riddled with bogs too
No, it's not particularly boggy - jmarkb's suggestion is a good one, it's an interesting and useful route. I've done the col-col thing several times over the years - not sure how many offhand, probably four or five, maybe half a dozen. Mostly S-N, having crossed Cruach Ardrain from the Crianlarich side and continued out to Beinn Tulaichean, as you did, then fancying a varied way back. I've gone the other way too, though, and it's nice however you do it. The two cols are much the same height (the CA-SG one is slightly higher), so it a pretty logical route as it's a fairly straight line although it does involve a bit of undulating to weave through various craggy bits. But it's all very easy, and if done in spring there can be some useful snow patches to cut a few corners. I've just checked a set of timing notes from a day in August 2016 and I got between the cols in 40 minutes - clearly timings are subjective, but I'm fairly sure however fast or slow one is it's faster than crossing Cruach Ardrain twice.
Incidentally, and it's a personal preference, but I'd much rather head up to Cruach Ardrain from the Stob Garbh col than go down the way - and I reckon I still thought that 30 or more years ago when I had better knees than I do now!