Hi Tezz
First consideration would be the type of shooting you want to do. The 38-55 is a good medium range cartridge with black powder loads and is quite popular in the USA amongst the silhouette shooters, who have reported good accuracy upto 500 plus yards. There’s plenty of moulds available to choose and from what I have read, MOA accuracy is possible with this load. However, I should point out my interest in this cartridge is strictly associated with black powder only. Though, I see no reason why it should not perform equally well with nitro.

I will not comment on the 44-40 and 38/357 as my experience and knowledge of these loads are extremely limited. I would assume these would be popular rounds for cowboy action shoots?!

Personally, if I was going to buy a single shot Hiwall as you plan to do, I would go with the 38-55 as it would fit in with the type of shooting I do. Conversely, if I wanted to blast away at close range targets with a repeater the latter would be given serious consideration.

ATB