The Ergo Prime "fixed" the one strong point of the previous design, the improved handle, and left all the frustrating bits intact. Way to go Lee! You took one of the gems in your product line and totally FUBAR'd it. The good news it that the only concern you will have with breakage on the two newer designs is you venting your frustration on them with a hammer. At that point I don't think that having a spare or spare parts will matter...
I suppose there are two schools of thought on hand primers. Seat with the thumb or squeeze with the hand.
I used the original Auto-Prime for about 30 years and I am probably used to the thumb method. Around 1980, the Auto-Prime was it when it came to hand priming. I would wear out or break about one a year, usually on a Sunday when everything was closed in the then Blue Laws state of South Caroline. So, the units were cheap enough that I kept two on hand, one for large and the other for small primers. Except the handle, Lee did correct over time some of the 1980 reliability issues.
I bought an RCBS Universal when Lee put out their warning to only use certain brands of primers in their Auto-Prime and to do away with using shell holders. The RCBS units prime by squeezing with the hand.
Probably due to decades of Auto-Prime use, I prefer to seat primers with my thumb. Recently I bought the Auto-Prime XR to try and I agree the primer maze and elevator is a bit Rube Goldberg. I do not like that the primer in the elevator is not captured at all times. I can see myself groveling on the floor looking for a dropped primer. I do that enough without the priming tool helping me.
So, I will stick with the RCBS unit for now.
There are a few instances where the RCBS Universal will not prime a case, brass 410 shot shells is the main one, so I keep an Auto-Primes around for those.
There is alot of personal preference when it comes to which priming tool to use. But, if you are budget minded, the Lee tools are reasonably priced so that having two is not a big hardship.
Final note, I do have two RCBS Universal priming tools, one set up for large and the other for small primers. I dislike changing the primer tools over and I have spares on hand in an emergency.