Re: Lee Collet dies and dead length bullet seating
A bushing neck die, used without an expander ball, and the Lee collet neck die will work the brass neck the same. Both force the brass only enough that it will spring back to the proper size. If you use an expander ball, then you are working the brass more. My only complaint about the Lee collet neck die (and the collet style FCDs) is that they are poorly finished, and usually need polishing the collet/closer interface to make them work smoothly and consistently. Good design, poor execution, but not so poor I can't fix it and have a great die to use (after I replace the lock ring too).
I have had very poor results with the Lee seaters, both dead length and regular. They use one seating plug for multiple bullet diameters, so they may work better for some calibers than others. There are much better designs (and executions) of seating dies available (Forster, Redding Comp series, Hornady, RCBS Comp, et al.)
Andy