Is the 135 flying as part of a crew, or single pilot?

Figure out what you want to do. Flying biz jets? Then do what is closest to it. In your case, that looks to be the 121 jet FO job.

Multi-engine, crew, jet, PIC - those 4 categories are the key to Biz Jets. The more experience you have in each of those categories, the better.

The best experience? Internal recommendations. If flying a Cub gets you face time with the right people, your resume will be at the top of the stack, ahead of my 1000's of hours of jet PIC, heavy, crew, international experience, etc.

It's all about who you know, not what you know.

You should consider posting in the non-121 forums if that's where you want to end up, not the regional forum.