I'd look for a used RCBS press in good shape...maybe an older cast iron job
cheaper than either you mentioned and sturdier than the partner imo![]()
The Partner is the lightest of the RCBC presses and is not overly robust. It is a light cast aluminum frame and while IMHO a better press than the entry level Lee presses it is far from being a cast iron Rock Chucker or Aluminum Reloader Special.
I picked a Partner up in a trade deal a few years ago and used it as a dedicated bullet seating press. I did try it to resize some rifle cases and while it worked OK I wouldn't want to do thousands of rifle cases with it.
I believe the Rockchucker Supreme is cast aluminum as well. At least mine appears to be.