I agree with ovrtake that the decision will have to come solely from you, but from my background, I flew piston twins for Cape Air and gained invaluable experience in IFR flying, flying up to 8 legs a day and building quality pic time before I got picked up by American Eagle and later a corporate gig. Sounds like Flight Express would allow for the same kind of experience, only difference is you would be flying boxes instead of people. Pay and probably QOL would definately put Flight Express in the "plus side" of the column.
In the end, you need to do what you feel will work best for you and your situtation. Good Luck!