Rather than looking at a month, consider a yearly overview and it may give a different perspective. This is a cut/paste from a post I made on a different thread regarding days off.
Just for a simple example..days off.
K4 - 14/30 (14*12=168 off/year) ATI - 12/28 (12*13=156 days off/year) [ATI has a 13 bid cycle/year for those who do not know]. A 12 day difference or what could be a half a month or more of work, again based on view. We all know individualistically, i.e. position/seat, vacation, where you live, luck, etc.... one's mileage will vary. Not meant to be pro or con, you be the judge of that.
Of course, mileage will vary depending on the individual (at any carrier). I believe it to be accurate that if you were to live in CVG, with ATI, your days off would be higher. There are "devils" in any details....in this example, ATI would consider you to be in your own city; therefore no hotel or per-diem (within a certain mileage). For more accurate info you would have to ask an ATI'er directly.
The point to be made was the amount of days off, by contract, without individual perspective.