I don't think the regionals will care how you got your ME time, as long it's legally logged and you have whatever amount they require (25-50 hours, I think most are 25 these days).

SP time is legal time. Be aware that you CANNOT log the entire flight since you were not SP or required crew during taxi, T/O, or LDG when the pilot flying was not wearing a hood. Also cannot log XC of any sort (XC requires a complete flight, and again you were not required crew for all of it). Those details are what might get flagged if an interviewer doesn't care for SP time.

Of course all else being equal if they were choosing between a guy with MEI time vs. SP time, I think the MEI would win. But today they'll probably hire both of you.