The best at what? 1000 yard F-Class? 2000 yard steel? 500 yard plinking? Long range hunting at more than or less than 800 yards? The die that is the best at producing the best F-Class loads might very well be building a round that is useless on a hunting trip because the tolerances are so tight that if the brass is wet or has some grime on it when you put it in the gun the bolt won't close. To get the absolute best loads in a completion you might need a mobile loading set up to adjust rounds the night before or day of the match. Heck you might need to load on the shooting bench to get the very best. Don't take all this the wrong way, it's meant to be an expansive look at why narrowing down to your own specific goals is very important to define what is best. Tell us what you want to be the best at, and that will drive the best dies to buy.
A custom honed FL die is typically better than a bushing die at runout, but you have to know the dimensions to order it in. And once you jump through all the hoops that custom die might not get you any better results than a bushing die or even a standard FL die depending what kind of chamber you're shooting it out of, and what the rest of your reloading tools and process looks like. A bushing die you can change over quicker if you end up with different lots of brass with different neck thicknesses. Are you needing to turn to fit your chamber? What are you going to expand with once you size? Mandrels or expander balls? What diameter of mandrel or expander ball?
You might not even have the best press already - the AMP press or a K&N precision arbor press with seating force pack both show the actual results of messing with interference fit in the neck. Without them you ultimately have no idea what is actually going on with seating force. So are you going to shoot 20-shot strings to get enough data to have meaningful results to interpret? Oh shoot, do you have a chrono to record everything with? Or are you doing to use OCW methods and find nodes on target?
And at the end of the day all of your hand loading might not even matter to getting on target. Can you shoot better than your rifle with factory ammo? Would you be better off saving the cost of those fancy dies and presses and using the money to buy enough components to burn through a barrel working on skills for your discipline, or shooting in field positions? Good excuse for a nice rebarrel if you have a factory gun now, and you can then match all your brass and dies to that barrel.
A Kestrel and range finder go a long way towards solving the two primary causes of misses - wind and range. Doesn't matter if you can stack rounds in one hole developing the load if you don't know if you're trying to hit at 400 or 800 yards.
A big part of the answer to all those questions above lies in how well you can measure what you're actually loading. If you're new to reloading the dies are pretty far down the list of "buy once cry once", and much more "it doesn't matter really, just get something to use" followed by "use the heck out of them". I generally think most people would be better off to start with a set of standard factory dies and spend money on all the tools you need to see what the dies produce - calipers, shoulder bump gauge, CBTO gauges, neck thickness mic, neck diameter mic, runout and concentricity gauge, and get really good at becoming consistent with all your measurements. That way when you have Forster hone out a die or you send Whidden some fired brass you know for sure what you're going to get back.
Nothing is worse than buying a new fancy something or other that you can't utilize to the fullest extent because another part of the system was really what was holding you up.
So what do YOU want to be the best at?
