It depends on what other guns you have.
If you are already a .45 ACP shooter, such as a 1911 owner, then I would opt for a .45 Convertible Ruger. This way you can use the .45 ACP cylinder. You get loads of cheap brass, and handy little speedloaders in the shape of 1911 mags:
https://i.imgur.com/Eru4bfF.jpg
While I am a died in the wool .44 Mag fan, it is hard to beat the practical nature of the .45 Convertible Blackhawk. The only downside is that sometimes .45 Rugers require some work, specifically getting the cylinder throats uniform, before they start shooting their best. That never really seems to be an issue with .44 Mags. With both S&W and Ruger, the .44 has always been a "Plug and Play" kind of thing. Plus I will say the .44 Russian brass/loads have been quite fun.
In fact I have a Manson chamber reamer floating around somewhere in PF land that fixes the throats on .45 chambers, and it is a pretty quick fix. So if you buy one, Just let us know and whoever has it at the moment, can mail it to you.