I had the old (old) Lee model with no tray, just hand feed a new primer for each case. It worked well but I eventually wore it out.

When I went to get a replacement, the deal breaker for me was that Lee keeps changing the shell holders with each new model and refuses to adapt to "standard" shell holders. I did not want to buy a whole new set of shell holders, so I switched to the RCBS hand primer and never looked back. I try to avoid "proprietary" items whenever possible.