The variation in bullet weight may be just that, due to something I did wrong in setup, if they were stamped the same. Normally, what I list as a 120 gr comes out at that weight if plainbase and a bit over 125 gr if gas checked. This because I cut both gc and pb the same length and the gc adds a bit of weight.
My 4 cavity molds are $175 each. If you want to get one of each, may I suggest that you get a little wider spread in weight? Also, have them both cut with crimp groove, or nose length to fill your guns cylinders out to the end. I makes a dramatic difference in velocity potential.