It would appear you have two options:
option A: Continue with Spirit. Although first year pay sucks the next two average $110 K a year with a 15% 401K DC. Then you upgrade and start logging PIC at 80 hours a month for $204 an hour and in 14 months have 1000 TPIC. Elapsed time - roughly 4 years.
option B: Take the DEC job. Get the DEC bonus, go through training for the same or different type, then go through upgrade training, and then go on Reserve, taking the dregs if the schedule as every FO who has the hours and cojones jumps over you in seniority while you make first, second, and then third year captain pay. Because counting going through training again, you’ll be three years getting to 1000 TPIC.
BOTH OPTIONS WILL GET YOU 1000 TPIC. My hunch is that 1000 TPIC of A320 time is going to be more valued by the other majors than 1000 of RJ time, but that’s only a hunch. The DEC option gets you the hours a year quicker but you make less money doing it. I doubt you are going to flow as quickly as you would get hired off the street in four years in any event, since flow generally goes in seniority order and though you make captain immediately, every FO on board when you get there is senior to you.
pick the option of your choice. It’s your career.