I have both those calibers and as far as ballistics are concerned I really never think about it and I use whatever ammo I can get off the shelf. I realize that doesn't make for good conversation regarding the subject, but I leave the writers in gun magazines to worry about that kind of stuff. When I walk over to the game I've dropped it certainly won't ask me what killed it.
The 38-55 regardless of bullet weight, or velocity is more than capable of taking out a deer, or even larger game like an elk, which I've never hunted, but would have loved to. The woods are dense and I'd say on the average a deer pops up less than 50 yards away. Now the biggy the .375 H&H. My H & H 375NE is also fantastic as well, but too costly for me to drag through the woods. I love the .375 H&H and love shooting it every so often. If it's good enough to take elephant, or any other dangerous big game in the world then what more is there to say. I'm sure many experts on the forum could be very informative and will certainly share some of their expertise regarding ballistics, etc.. I have my .375 H&H specifically for bear, but unfortunately never seen the damn things while hunting them. They tend to pop up when least expected.
Both calibers are proven to be very capable. Here's a couple of mine. This is a '94Winchester SRC in 38-55 mfg in the 20's that put meat on the table to feed the original owner's family in the good old days when it was really depended on. It's been good to me as well and a pleasure to carry in the woods.
This is a custom German mauser .375 H&H, re-barreled w/ matted receiver by Griffin & Howe after WWII with an engraved G&H mount and rings, Lyman Alaskan 2 1/2 power scope and double set triggers. It has a spoon bolt and one raised and one folding rear sight.