Best of luck in your decision. Here's my .02c .
First off, if you have that much TT and are training people everyday, how in the world do you not have your ATP yet?? You obviously have access to planes, you must know plenty of examiners, and money is no issue... Get your ATP ASAP. That alone will make you more marketable.
I'm not from the part 91/135 world, but from reading here and talking to friends, networking and "who you know" is everything in that market. I can guarantee you this. You go to a regional, you will never see that side of the world! So if You want to stay 91/135, stay there and keep making connections. Seriously. I'm not trying to be a downer or condescending, but don't go to the 121 world hoping to get a 91/135 job.
Best of luck.