As said before it's your chamber. I debated the same thing about dies. Ended up with 4 sets for 6.5 CM. I have a few CMs so it works out.. Here it goes as far as seaters.
I bought Redding premium series set with micrometer seating stem, A Forster set with micrometer seating stem, Hornady and lee. I like them all. I like how Forster supports the case, but they do have a problem with the stem. It can crack. They tell you not to use it with compressed loads and it's for a reason.
The Redding is ok but like the Forster micrometer better.
Hornady kind of copied Forsters seater design some what but it doesn't really work the same due to you can use it for any cartridge with the same bullet diameter. It doesn't support the case. It's accurate enough though.
I find myself using the lee more than anything else. It does t look as pretty but Dead set seater is the proper name for sure. It has less run out and seats it dead on every time. I wish they had a micrometer option. It's a great set and forget seater.
All the FL dies work the same. Some look better than others finish wise but they all work the exact same unless you use Bushing dies. I have a few different bushing dies for necking up and down wild cats but to use it too set neck tension isn't worth it. Not all brass is created equal. Unless you have Lapua or something similar you will find yourself buying several bushings which adds up fast at $15-$20 apiece. Different brasses have different neck thicknesses and you can have neck thicknesses all over the place with the same manufacturer unless you neck turn. Not worth it unless you're shooting competition.
Good luck