The Dillon has been on the market a long time and have great customer service, as a result, Dillon users are extremely dedicated to their blue presses, which is as it should be with satisfied customers. The Dillon's are EXCEPTIONAL presses and do an exceptional job in reloading. The guys that have Dillon’s are very satisfied. The competition to the Dillon is the Hornady Lock and Load Auto Progressive. Because most of the Dillon users are so satisfied I was swamped with comments like, "The Hornady L-n-L is Junk!" I asked if they had ever loaded on the L-n-L and 99% said no. When I did find someone that had experience with both presses, most liked the L-n-L and many had sold their Dillon's and bought the L-n-L.
IMHO the Dillon has one major shortcoming and most Dillon owners will agree if they are honest. The Dillon powder measure is sorely lacking in ease of use and adjustability. It meters ball type powder very well but flake type powder less so. And, extruded stick type powder is VERY troublesome and not all that accurate. To be fair, extruded powder is difficult in all powder measures. But, the L-n-L powder measure handles all types of powder MUCH better than the Dillon. Also, it is a pain to swap out the Dillon powder measure to another die plate. As a result, many owners have several powder measures on separate die plates for changing calibers. This significantly drives UP the COST.
Also, the Dillon gets filthy as the old primers are caught in a cup after they have rolled off the side of the press. The L-N-L spent primers are dropped thru a plastic tube and into the trash or bottle or whatever you want to use. The point is, the dirt off the spent primers does not foul the workings of the press. As a result, the L-N-L IS MUCH CLEANER TO USE THAN THE DILLON.
The Dillon 550 has 4 die stations and the L-N-L has 5 stations. The Dillon 650 has 5 stations but, costs significantly more. Also, the Dillon 550 does not auto index, the L-n-L does. The Dillon 650 DOES auto index, but again, at more cost.
Next, the L-N-L uses a really slick bushing system for mounting loading dies to the press. It makes changing calipers and SNAP. After a die is adjusted for whatever you are loading you can remove the die from the press with an 1/8 turn and insert a different die. Each die has it's own bushing. The Dillon uses a die plate. The Dillon die plate costs more than L-N-L bushings. Another neat feature with the Hornady is that you can buy a bushing conversion setup and use the same bushings on your RCBS, Lyman or other single stage press and the L-N-L!
Additionally, the L-N-L seems to be built like a tank! The ram is about 2"+ in diameter and the basic press is similar in construction to the RCBS Rockchucker. I would say that a side-by-side comparison to the either the Dillon 550 OR 650, the L-N-L is at least as sturdily built. And, In some areas I think the L-N-L is better built. i.e., The massive ram, powder measure, and primer system. The head/top of the press is solid except for where the dies are inserted. The Dillon has a large cutout that is needed for their die plates. By just looking, it would seem the L-N-L would be stronger. But, of course, that may not be the case.
There is one piece that can get damaged on the L-N-L. There is a coil spring that holds the cases in the shell holder that can get crushed if you improperly change shell holders. That's the bad news. The good news is that they are only about $2-3 and they won't get crushed if you change shell plates correctly. The other good news is that this spring is the primary reason that while loading you can easily remove a case at any station. With the Dillon you have to remove pins in order to take a shell out of a shell plate.
You can load anything on both the Dillon and L-N-L from .25 ACP to 500 N.E. Realistically, I would say that people with progressive loaders mostly load pistol ammo about 99% of the time. After using the L-N-L for while I feel confident that my Grandkids will be using when I'm gone.
In summary, the Hornady L-N-L has all the features of the Dillon 650 but is much cheaper. Changing calipers is faster and cheaper. The powder measure on the L-N-L is VASTLY SUPERIOR TO THE DILLON, at least in my opinion. Hornady has changed the design of their powder dies and now allow case belling and powder drop at one time, just like the Dillon. I bought the L-N-L and am very satisfied. A shooting buddy of mine is a long time, dedicated Dillon user. He has three! After giving me a ration of "stuff" about my choice, he came over and used my L-N-L and sheepishly said, "That's a very nice setup!!"