I got caught up in the simplistic argument that you can save money by using reloads. So I had to check it out for myself. I made a spreadsheet of options (Estes, Qjet, Aerotech single use, and RMS) for motor classes D through G. But before we get to that, I should mention that after using RMS, I found that there are some valid reasons to use them other than cost. More on that in a bit. What I found:
D: Estes best, Qjet second. The 24/40 is more expensive, and really has little to offer other than the ability to adjust delay. Unlike the E26, I like and use the D22.
E: Again, Estes. Then Qjet, with 24/40 not far behind. However, I don't like the Qjet E26, I've had lots of problems with them, and the thrust curve is a bit "soft", with the rocket coming off the rod slower than the other choices, unless it's quite light. But the RMS really shines here because the E18 and E28 are much "bigger" in total impulse than the other 2 and have more punch off the rod. Especially the E28. So my choice here mainly centers on the particular rocket's motor retainer system. There are also E motors available for the 29/40-120, but I can't see the advantage, as they are much more expensive.
F: Hands down, the 24/40 is far cheaper than anything else. But all the choices are "baby" Fs, all less than 50Ns. There are slightly bigger choices in the 24/60 case. For mid-F, I'm using the F67 single use, and if I need something bigger, the 29/40-120 Fs go all the way up to 80Ns. However, you have to plan the purchase of them, they are all Hazmat. I get them at club launches.
G: RMS 29/40-120 is the only way to fly. As they split the grains in two, they avoid Hazmat on these. Puzzling, as there is still the same amount of propellant in the bag, sitting right there next to each other, they are just not in one chunk. If they caught fire, I'm sure they'd both burn.... There are Enerjet Gs, but they are more expensive and Hazmat.
Now the other considerations. First is fuel choice. Most RMS sizes offer the regular White Lightning and the faster Blue Thunder. However, the 24/60 also has available the smokey Fast Jack and Redline. I first scoffed at this until I saw a Redline take off. It looks like Darth Vader's lightsaber sticking out of it's butt. Way cool, worth the extra few bucks. And the 29/40-120 has a Mojave Green option. It's a neat flame, but you really need a camera photographing the liftoff to do it justice. Second consideration I already mentioned. You get more flexibility in delay setting.
Just my $0.02, and with inflation, that's not worth much.
Hans.