Short answer, buy them all. They're all cool and each have historical significance.
Caliber wise, bbviously the 44 is going to be more powerful, but the 36 is a known nail-driver.
The 44 Walker and Dragoon were considered the most powerful handgun till the advent of the .357 magnum in the '30s.
The 1851 Navy's was incredibly light compared to the Walker and Dragoon. It featured a strong, octagonal barrel. It slipped easily into the belt or holster and could be drawn with ease. The caliber was hard-hitting yet recoil extremely manageable. As such, it was favoured among the earliest gunslingers or "shootists" of the Old West, most notably James Butler "Wild Bill" Hickok.
The 1860 Army was the finest of Colt's cap and ball revolvers, both in power and function. Due to advances in metallurgy, Colt was able to utilize the frame size of the Navy revolver, but up the caliber to the much more powerful .44 of the Walker and Dragoon. The revolver featured prominently in the American Civil War, most often seen on the belts of Northern officers.
Loads are readily available from most of the manufacturers you mention.
I would caution you against any brass-framed revolver. They simply aren't as strong as steel and aren't that much of an economical savings in the long run.