My opinion but please ask others
Tycer,
If it is Southwest where you want to go, I would recommend that you continue to get PIC turbine time. The day you get downgraded, everyone else will be getting more and more competitive relative to you. Which ,in effect, will be delaying your interview date. Also, consider getting the 737 type since they have said that they will be calling typed pilots first (according to SWA PD 95% of interviewees have types).
I don't know if you have flown 135 before but if you haven't I think the experience will be a definite plus IMHO. You and your copilot will have many more duties like baggage handler, cook, flight attendant, flight dispatcher, pilot, janitor, accountant, cleaning technician, DJ, movie DVD operator, psychiatrist, ramp agent, bartender,etc... Most likely you will go to different, unfamiliar airports all the time and enough things will happen which will generate even more stories for your interview, giving you more depth as a candidate. SWA is a company dedicated to the highest quality of customer service and I can not think of a better environment in which to get customer service experience than flying Part 135.
Believe it from a pilot that's bailed out a few customers from Mexican jails...oh yeah, forgot to mention...lawyer