Like has been mentioned, stick with the 12'ish BHN range and you will be fine, no need for harder. I am shooting less than that, and to the 12-1300fps range loads with some plain based loads in my 41, 44, and 454, and not loading up my barrels with streaks of lead.
As for the design, either will/should work well, just more of a personal preference than anything. If your planning on reaching out to 75 or 100yds you might go with the Keith SWC designs, of staying under that and possibly hunting with it the RFN's are great.(might have the RFN SWC range thing backwards, I do that sometimes)
If your possibly looking to start casting your own, the Lee .452-255, is a great one to start with. It shoots VERY well from my Ruger 45 Colt with standard or Ruger only loads. It also is quite a load in my 454 as well. Even if your NOT looking to cast yourself that particular design is a GREAT one for most 45 Colt loads.
Do yourself one small favor, ok maybe two, pick up a package of the copper Chore Boy pads, (make sure they are copper and not copper plated steel) and also possibly pick up one bottle of Lee Alox. "IF" you find the bullets DO lead, you can pull one strand off the Chore Boy pad and wrap it around a 45 cal bore brush and it will help cut the lead out quickly.
Again, "IF" you find that your bullets DO lead, don't give up on them just yet. Give them a coat of the Alox first, and give it another go, just coat right over the factory lube. IF you feel up to doing a little mixing, you can use the 45/45/10 lube made up from the Alox and some Johnsons Paste Wax, which dries to a non sticky finish. Also with the Alox, a little bit goes a LONG way so don't use but a small bit, about a thumb nail sized glob will easily do 50-100 bullets. Folks say if you can see the difference in color on the bullets you used too much, I usually use too much. Just figure that to a point a little more doesn't hurt, smoke more yes, but doesn't hurt.
The Alox is only around $8 a bottle, which to me is not much to give somethig a try especially if it helps out, and your not scrubbing lead, plus one bottle will lube who knows how many bullets. I use the 45/45/10 version on everything from my 38SPl's to my full tilt gc'ed 454 and have no issues with leading what so ever. Lucky, maybe, but I don't figure luck would carry through across all of those loads and calibers without the lube doing it's job.
If your interested in the 45/45/10, you can find the info on it here,
Tumble Lubing--Made Easy & Mess-Free
There is also a LOT of info on the 45 Colt on that site as well.
As for powders, Unique is a good one, it will be a bit sooty at the lower end loads. The Accurate powders #5,7,& 9 work well with this round, as does HS-6, W-230, and a few others. Some mention that Universal can be used almost as a direct cross over for loads using Unique and burns much cleaner. I haven't used it yet, and if I DID I would work up accordingly. I have however burned plenty of Unique and the Accurate powders and HS-6 all with great results. With my Ruger even shooting the standard Colt loads I haven't found anything to date that I would call unacceptable, but some loads have shot a bit better than others.
You might also play with a couple of different primers, as some like the Winchester might be a bit much for some loads, where as the CCI, Federal, or even the Wolf LP, are perfect. Sometimes the Winchester, even though it is a great primer, has a bit more to it than is really needed with some powders.
Hope this helps.
