Doing a detailed comparison is reasonable, just make sure it's a fair comparison.

21 Air pays 6 hours per day for every day away from home. That's 108 hours of pay if you work a 18 day month, regardless of how many hours you fly. 12.5 days of work and you're at the 75 hour guarantee. Do the math! Also, full per diem from the time you depart your home airport.

Upgrade at 21 Air can be very fast for those with the required 121 hours. Getting on the CA pay scale sooner should certainly be considered in the pay calcualations.

ABX pilots need a crashpad or hotel in CVG, in most cases. This should be subtracted when making any comparison. Jumpseating/traveling is also done on the pilot's time, which should also factor into the calculations......"working for free" versus getting pay and per diem for all time away from home. Do ABX pilots get per diem when sitting in CVG? 21 Air pilots do!

If you're planning on stagnation in pilot hiring at the majors and many years at your next job, K4 and Atlas may be better long-term options.