8 out of 10 times, my "grab and go" is a cigar. I'm not grabbing a pipe and going with anything I'll go nuts over if I lost or destroyed it. But forgetting the pipe and cigar, and addressing just the tobacco as was the question, the consideration is whether I'll be with others who don't smoke, and if so, I'll go aromatic. If not, something more substantial, but either way, I'm going with whatever I happen to have in preferably a pouch, or a small tin.
There is no certain blend, although now, I have Ashton Artisan's Blend (a medium English) in one roll, and the other roll is ready for either MM American Patriot, a Latakia-Burley blend (a "LatBur"?), or if I need to be smoking an aromatic, for Peterson Conoisseur's Choice.