If you take the 135 gig, stay on them about the upgrade, even after 6 months. 500 hours (1000 is better) of PIC turbine is a good box to check for other jobs. Sure, there are legacy airlines in which there is no official PIC turbine requirement. However, you'll be more competitive.

As for which one, I'll just say that 135 time will make you a better and well-rounded pilot in the long run. Also, having 135 or a corporate background will make you more competitive for more interim flying jobs when you get furloughed from an airline. After you get your 135 PIC turbine time, go to some regional to check the glass/121 box and you'll be golden. Barbie jets and the transition to glass will be easy after flying a King Air around.

After the newness and honeymoon phase is over (strangely, this seems to happen when you see your first pay-stub), regional flying will suck the life out of you and it will be challenging for you to stay optimistic about your airline career track.

Either way, good luck.