I use ball powders and WST powder for my pistol loads. The Dillon powder measure works very well with these powders. I like using the equipment a press comes with. Since the Dillon press comes with a powder measure and that measure works so well with the powders I like using I use it and I don't look for something else. The Dillon powder measure is very easy to adjust and use in my opinion.
I have a RCBS set of dies for one caliber I load. It does work. Occasionally I do have to re-position the case for the sizing die. I don't have to do this with Dillon dies. It is a slight inconvenience. I get good ammo with RCBS and Dillon dies on the 550b. I'm pretty sure you can get good ammo with other standard dies sets too.
If you have a Lee powder measure from another Lee press setup, I suggest keeping it with that press so you can have two presses set up to load different calibers. The Dillon is capable of producing pretty good volumes of ammo per hour. Probably more ammo per hour than any Lee press. I don't need that high of a volume for every caliber I load. A slower press still has value even with a progressive press on the bench.