Be prepared for lots of comments.
The only two loaders I've used much are the MEC 600 JR and the Dillon. I think the JR is a great loader to learn on, but not suitable for loading in any quantity. My recollection is that it would take me at least an hour to load 100 shells.
I bought the Dillon used from another poster on this site, and soon had my first experience with Dillon service. The seller had disposed of his boxes for the press, so called Dillon, and they sent him a set so he could ship it to me, no charge to either of us. After I set up the press and loaded some shells on it, I broke a part trying to force something when I shouldn't have. I called Dillon's 800 number and explained what I had done. I told them I was not the original owner, and that the breakage was my fault. Their response was it didn't matter, it was a Dillon, and they stand behind it. They took my contact information to register me as the owner, and sent me the replacement part and a spare at no charge, not even for shipping. Whenever I've called the help line I've received knowledgeable information, and any parts I've needed are sent promptly, no questions, and no charge. Last year I had some issues I could not fix, including the motor on the shell feeder that would run very slowly until it warmed up. I called Dillon, got a return authorization number from them, and sent it in for an overhaul. The press was returned to me fairly promptly with all the issues fixed, and all I paid for was the shipping to them. No charge for the service, return shipping at their expense. Understand that they do not make the motor, and the manufacturer does not guarantee it for anywhere near as long as my press is old. Dillon replaced the motor at their expense. Nobody has a better guarantee or service than Dillon! Nobody!
As to the specifics of the press, it is as fast as anything I've seen. It can easily load two flats or more per hour without rushing. Two items that are absolute essentials are the shell feeder and low-powder sensor. With the shell feeder, my right hand stays on the handle, and the left loads the wad into the wad arm. Both the powder drop and shot drop stations are case actuated. If there is no case in the station, no powder or shot is dropped. I can usually tell by feel whether a primer has dropped and been seated in the case. Almost all the time it happens, but if it has not and the case has been advanced anyway, there is a mess to clean up when the case is advanced to the next station and the powder spills through the empty flashhole. If I start a stroke and something hangs up (like a wad on a bad case mouth), I must either complete the stroke or stop and unload the stations. The reason is that once a stroke has been started, reversing the arm advances the platen and dumps the final shell which has not received a final crimp, which spills its shot. Completing the stroke usually crushes the offending shell and makes a mess too. However removing a shell from any station is easy, so the solution is just to stop the stroke, remove the non-affected shells, reverse the stroke and remove the affected shell, reinsert the other shells into their proper stations, and move on.
Unlike most other presses the Dillon does not use bushings. Both shot and powder settings are completely adjustable. If I want to load one ounce of shot and 16.5 grains of Clays, I get out my electronic scale and set the press to deliver that. Once it is set, the amounts dispensed are very consistent.
If you buy one I suspect your biggest problem will be the same as mine - I'm always running out of something. Right now I'm down to one bag of shot, no primers, half a bag of wads, almost out of an 8-lb jug of International Clays, and a few hundred empty hulls. On the other hand I've loaded over a thousand shells in a couple hours over the last two weeks.
If you want a great press with customer support second to none, get a Dillon.