I think any name brand loading die will do you just fine.
I have no experience with RCBS Cowboy dies
http://www.rcbs.com/equipment.html
but have loaded an awful lot of ammo on their regular dies, .357 cast and jacketed included.
Lyman is good, CH and Lee are OK. Redding has a terriffic reputation and I know a happy Bonanza user. I don't have any Hornady dies, but have read that the titanium nitride coated band in the sizing die serves the same purpose as everybody else's carbide insert - no case lube required.
I would get dies listed as .38-.357 so you could handle .38 Special brass if the need arose. Even if they are not marked for both, you can load Magnums with any Special die set I have ever seen, but not the other way around