That's the little turret press designed to use 310 dies, right?
I have one, haven't used it yet. Mine came with two tool heads, one for 310 dies and one for standard 7/8x14. I got it planning to load .22 Hornet one which I only neck size. That is a diminutive little press for a big ol' case like .45-70.
Generally I would agree with your statement and I do not own RCBS Cowboy dies for .45-70 (yet) but have them for several other cartridges and am convinced they are better for loading cast and worth the extra cost. The switch to them made a very dramatic difference in how my .38-55 loads shot.