If gun weight is a concern to you for field carrying, and you don't think you will ever really need the full power of a 44 Mag, then the Ruger 44SP flattop has some distinct advantages. It is, or at least seems, lighter and much easier to carry than a SBH of comparable barrel length. However, you will only realize it's advantages if you are a handloader.
Otherwise, if you need full power of 44 Mag for hunting, you would probably prefer a SBH because of the availability of more ammo choices.
Ditto the 45 Colt. It is a great round, but expensive to shoot if you only use factory ammo, regardless of power level, and it is not something readily available at just any gun shop or big box retailer, especially the specialty loads that take full advantage of the Ruger's power handling.
If you handload, pick whatever one you want based on the gun, if you don't and don't intend to, then pick the gun based on the ease of obtaining a variety of ammo and its availability.
I really like the 44SP and have a number of S&Ws and 2 of the Ruger Lipseys. Although my 3" Lew Horton S&W Model 624 and 24 are great guns, and the 696 has some advantages as a woods carry gun because it is a DA, the Rugers are the 44 Specials that have really caught my attention most. It is a great cartridge in the right gun! I'm glad it is still around.