There are so many variables that it really depends on the two companies in question and your personal situation.

Which company is more likely to be stable in the storm ahead?

Does the 135 operation have a business model which is immune to fuel costs (air ambulance, military, etc)?

What is the schedule at the 135 op? What kind of lifestyle do you want?

You will likely be on reserve for a while at most regionals.

If you have a family, look at the safety record (and your gut feeling) of the 135 op. Despite all of the bad things about regionals, they usually return you home alive at the end of your trip.

Here's a thought...do both! Take the regional job, get trained, get furloughed, and THEN do the 135 gig If you like the regional better, accept the recall, if not...stay put.