Upgrade = FO to Captain
If you want majors, getting to Captain and loggin turbine PIC time would be invaluable. Although I've read that some majors will take turbine SIC at par. Airlines like jetBlue won't, however. They want to see that you've logged 1000 hours of turbine PIC time (along with a boat load of other time requirements). Corporate outfits will want to see that you have their minimum requirements. Suffice to say, logging Captain time will definitely make you more marketable if competing with an FO for the same job.
You can go regional or corporate today, depending on who will hire you with what hours you have.