I use the Small Base RCBS Dies because I got them at a good price. When I started loading the .300 Savage bulk factory brass had not become an item on the market as it is today. And factory loaded ammunition was getting hard to find and it was always at full price. The .300 Savage became the idea round to load. I purchased a couple hundred rounds of once fired NATO 7.62 machine gun brass. With the brass came a paper saying the it should be resized with Small Bass Dies. The brass has worked out great.
So many years down the road finds that I have a lot of brass for the .300 Savage from a number of sources, once fired factory, Military, and recently my brother gave me a bunch of new Norma .308 Winchester brass.
Over the years I read recomendations that Small Base dies be used for autoloaders, pumps, and level actions. I do not think they are a must have item if you stick to factory brass fired in your rifle.