I have two sets of .40-65 Win. dies. One RCBS and one Lyman. I think they're equal in quality, and work equally well. 
I'd simply buy whatever brand you prefer to own.

It sort of depends on how tight a chamber you have and which brass you are using and what your groove-to-groove diameter of your barrel is.

Also the diameter of your bullet can also make a difference on how tight the neck tension is.

Some people have had trouble with Starline brass being a bit tight at the web for the tight Shiloh Sharps chambers whereas Remington cases had a bit narrower web.

They use the .408 Shiloh Sharps RCBS dies to FL size the cases down.

I use fire formed Starline cases; slightly bell them, and load a .410 diameter bullet and then crimp them using the Lyman .40-65 Neck Die (with the depriming rod removed) for use in my 1874 Shiloh Sharps.

Any manufacturer of .40-65 dies will work quite well for you; unless you have a tight or Match style chamber or you need to use the smaller diameter bullets (.406 vs. .408).

Then best to get the .408 Shiloh Sharps RCBS dies if you want to FL Size your cases instead of using fire formed cases.

Other shooters have indicated the Redding dies have a much tighter neck; much more neck tension or designed for smaller diameter bullets.

Some have indicated the RCBS Cowboy dies are for the smaller diameter bullets (.406) as well.

As I am contemplating buying a C. Sharps in 40-65 from a local guy, this is a useful conversation for me. An entirely new venture for me, so there is much for me to learn. The rifle is described as having a "Shiloh match chamber", so I too am curious how I would proceed with purchasing dies for it. If I buy it.....

The 30" barrel is described as a "Badger full octagonal".

Thanks for the information. The Tex-mac article was very informative. The rifle is in progress. I will contact the gunsmith and have a chamber cast done.

That was some good reading Bob, Thanks.

I'm suddenly wondering how I've gotten so lucky to just buy a set of RCBS dies and have them work for loading all sorts of .40-65 dies?
Whether it was original .40-65 brass, or reformed .45-70 brass, they've always worked just fine in my single shots in this caliber, and now after reading the info I wonder why?
Just lucky I guess.

I think it just depends on who cuts the chambers Val.  My first Shiloh, when using the RCBS Cowboy dies to size the brass, did not reduce the base of the case enough.   The cases would chamber, but needed some effort to get them all the way in, and required some force to extract.  The RCBS dies specifically for the Shiloh took them down just a bit more so they fit perfectly.   This of course makes perfect sense since RCBS made these dies specifically for the Shiloh Sharps chamber.

Chris.