Of course the firearms are more interesting, but I think comparing the cartridges is also instructive.
That big .50 is something; the hand cannon and the cartridge. I don't want one; .44 mag is as hot a handgun as I ever want. Though I have wondered about a single shot Thompson Encore in a rifle cartridge just for fun.
My American Derringer is .44 mag. OK, I didn't go looking for it, but there it was on one of my buddy's gun show tables. And the price was right. And it completed the set of cowboy-esque .44s; Marlin 1894, and three screw-Super Blackhawk with tie down holster, and a derringer for my vest pocket.
It is not fun to shoot the derringer with 240grFMJ. If you don't hold it real hard, it will leave your hand when fired. It's not bad with 180grJHP .44 Spls. And I have a pile of hand rolled #12 bird shot rounds which are practically recoil free. I patterned the bird shot rounds, and at about 20 feet, I'll hit you in the face and the shoes in the same shot. At any distance, it's not a man stopper, but it will make you say oweee. LOL

I decided sometime back, I would not add any new calibers to my collection. So I often think backwards these days and look at new firearms that shoot calibers I already have, like a Thompson Encore Pro Hunter in .223. There will always be more 223/5.56 at my house than any other. But the dang thing is spendy.