Best is such a relative term...best period..best for the money?
Having used most popular loaders, Mec would have to be hands down best loader for the $. I used a grabber, then the 9000, then added the original automate. Other than letting a piece of shot slip into the collet, or the dreaded tipped primer (got it down to very few, but still had to watch it like a hawk), it was a great loader. I had both old chain style and new larger style primer trays.
I got the P/W 800+, great loader. It was temperamental, and mine perhaps was made on a Friday before a 3 day weekend. I had primer feeding issues right out of the gate that turned out to be a poorly cut primer ram, but it was frustrating to say the least. Powered that by hand, original automate, then hydraulic.
I have a Spolar with hydraulic currently. No clue if it will ever in my lifetime provide a payback, but there is no comparison to loading pleasure. It works, works well, rarely misses, and when it does, it was operator error. Primer feed is bullet proof as it can be. Powder drops are dead on every single time. Same with shot, which their shot bushings actually drop the correct grains. Crimps are fabulous, but honestly so was my P/W unit.
I am anxiously awaiting with others to see the new P/W unit that is due out shortly. I miss the hull feeder on my 800+, hoping their new mouse trap will have all the bells and whistles, but most importantly, just load shells without any issue. If it looks like it will do that with the electric drive, I will need to fire one of those up in my room.