Whose dies to use?
As Mike & CD said, any company's dies will work and there isn't a lot of difference between manufacturers, for a die of a particular purpose. I like RCBS dies, but that's because that's what I happened to start with. Buy whatever brand of die is easiest/cheapest to obtain for you. You will develop your own preferences.
The Lee collet neck-sizing die is in a class by itself as far as I know. It does not crimp the case necks, and is intended to make ammo for bolt guns out of cases fired in the same gun. Lee guarantees you it'll make the most accurate ammunition you ever reloaded if directions are followed. You do have to follow directions. When I got my first Lee Collet, in .30-'06, some years ago, their directions were not too clear on the point of exactly how far down to screw the die into a RCBS rockchucker press, and how much pressure to apply. Ruint the die on my first try. Sent it back to Lee with a letter of explanationÑTWO DAYS later I had it back, fixed, no charge, with a letter explaining how to avoid the difficulty. Lee has since changed their instruction sheet and the problem I encountered is easily avoided following their directions.
A nice thing about a collet resizing die is that you don't have to lube the cases when using that kind of die, so you then don't have to clean case lube off the brass. That is a big plus, for me. I find, though, that the mechanism itself wants a tiny dab of grease, on the camming surface that shuts the squeezers on the case neck, so the die needs to be disassembled to do that, at the start of a production run. Doesn't cover this in the instructions. Greasing avoids the squeezers sticking shut, so when you run the next case in, instead of sizing the neck, the die ruins the shoulder of the case. Found this one out the hard way. And this is still far less hassle than cleaning all the cases after sizing. (BTW, "squeezer" is an advanced technical engineering term. I don't know what that part is really called.)
As to accuracy, I loaded up a number of .30-'06's, using all identical loads, half using cases that had been through my RCBS resizing die, half using same manufacturer cases (happened they were Rem) that had been through the Lee collet neck sizing die. Out to the range with 'em, and my trusty sporterized '03-A3, and sure enough, the Lee-sized loads clearly had a (small) edge in accuracy. Since that experiment, I seldom use any other die for making '06 ammo. They work in my friend's pump Remington '06 also, with fired cases from that gun, but this is not to say they'd work in any other pump; you'd have to try it and see. And of course it'd have to have a box magazine, as a tubular mag requires crimped ammo.
Have since gotten Lee collet dies in .243 Win, and most recently in .300 WSM (They don't offer it yet as a standard item; this was a custom job).
Lee's website is <
www.leeprecision.com> where they have a complete catalog. You hear various bad things about some Lee products, some of which may be true. But I have never seen, read, nor heard anything bad about Lee die performance.