I find with the digital ones, no matter what name is on them, they all come from the same place. I use westward digital calipers but I have seen many other brands that are EXACTLY the same all at different price points, from $150-$20
I've been using a pair of 4" Mitutoyo dial calipers since March 1970. The zero has been reset about a dozen times at most. Takes about a minute and a half to do this. I also have two or three pairs of Starretts and at least one Brown & Sharpe, and who knows what else (think I have eight pairs). I do not like the Starrett dial calipers because of the crap you have to go thru to reset the zero. Accuracey wise they all seem to be about the same. They all are .001" measuring devices no matter what the resolution is. One nice thing about the Starrett digital calipers is that you can slide the battery cover about 3/8ths of an inch thus disconnecting the battery and making it last a lot longer. B&S maybe that way as well. All my Fowlers were different, and you had to completely remove the cover. I wish somebody would sell a pair like the bigger Fowlers and B&S that had pins on the top side for making measurments in I.D.s on small holes. The blades are not accurate
+1 on the mitutoyo. I use them at work for measuring clearances on precision bearings as well as at my reloading bench. I find that the 6" ones seems to give the easiest use for me. I do have a caliobration block that I used to use to check it with but quit doing it as it never seemed to be out in the 3 years or so that I was checking it.
You say your caliper won't hold zero but you don't tell us which kind you have and that matters. If it's digital you may have a defective bit of electronics so toss it. If it's a manual you may need to clean the surface of the jaws; invisible stuff can prevent them from closeing properly.
I've long had a Swiss made professional grade 6" caliper but it was expensive and if it gets dropped on a concrete floor it will convert to expensive junk. SO, for my reloading I've been using the cheapest Chinese calipers I can find, usually some $9-12 at Harbor Freight Tools when on sale. The digital version has been on sale for $9 in an add in the Am. Rifleman the last couple of months; that's an excellant value for reloaders.
I do some machine work and now have four Chinese dial calipers and a digital, they are exactly the same tools sold by the reloading companies for three to five times more. And all of are well within the accuracy needs of a reloader, as well as most machinests; mine are off no more than a half thou and are much closer than that at most points. If I should drop one, who cares, I can get a dozen or more for the price of a single profesional grade tool.