I personally have only worked with the 300 RUM while helping out Tim when he got his. We tried several of the above mentioned powders. At the same time I was also working up loads for my .270 AM using the 872 and 869.
The thing we found with most of the loads and powders we worked with was, we could not get close to the charges most are using with some, but could get better with others. I don't feel that this was more due to extreme differences in powder lots, than differences in where we are, compared to where most here are.
We're still getting the velocities that most are, but the climate here is such that some of the popular powders will max out generally 4 - 6 grs below what some are using. The H-1000, was the winner for his RUM and so far I have settled on a load with the AM using 92.5gr of 869 for a 3260 velocity. The RL-25 which we tried three different lots of was the worst case of this. Loads would go from good to close to blowing the primer out within hours of loading them . Just due to the temps and changes in humidity. Yes they were up there, but were fine at 65 degrees and blowing primer pockets at 85. It works great for others, but not for the area we hunt and shoot in.
I am now working with a 7 STW and am finding the exact thing mentioned above. Similar powders showing differences of a couple of grains going from mild to mean with just a change in temps and conditions. The trouble is we go from winter to summer on a weekly, and somtimes daily basis, not to mention that you can actually see and feel the humidity change from a nice 40% up to 70% plus and the temp remain fairly constant. Just takes a shift of the wind and a few hours. Not to mention the pressure swings as a high system moves through followed by the rebounding low system. FWIW - it seems when you get case capacities above the 70gr mark, that the powders used take on a whole new character. I can shoot any of the Reloader powders in my standard 7 mag, or smaller cases with hardly any noticable change in things, but once you get above that limit things start to differ.
The folks who live down here in the balmy South should realize that the humidity and lesser altitudes play an important role when you get up in the bigger powder charges using these slow powders. I conversed with Lerch and Bill both while working up my loads and I still could not get up to the charges they were using, but then again, they are some 500 or so miles north of us and their climate is different.
My recommendation would be for those of us in Tx to try to work up your loads on those mid June and July days when you can spit steam, and the humidity is dripping off the roof. Then you know your set for our terrible 30 degree winters. The coldest day we have been able to shoot in was around the mid 30's so far, and it only changed the drop about 1" at 500yds on our loads. We weren't able to check the velocity due to the rain but figure it is only a matter of time before we will hit a clear morning and similar conditions.
I do know for a fact that I shot some of the 869 in June, and it was in the mid 90's, that trip I put a couple of rounds into the ice chest we had our drinks in and dropped them down to around 65 degrees. I noted a drop of 200fps between the ones I had sitting ambient temp in the box and shaded. I also know that this works just the reverse as I ironed out a couple of case heads, (primers were toast), just a short time before then with a similar load.
Just some tid bits I thought I would share. Bottom line is like GG said, the powders will tell you which one is going to work. You will have to determine how it is being effected in your rifle under your conditions in the areas you live. What works here or there might be on opposite ends of the stick. If your headed from the flatlands of the Gulf Coast to the peaks of some mountian range, the best you can hope for is to try and meet in the middle. One thing for sure, if your load is on the upper end down here, your probably fine going up, but the opposite isn't always the case.