It depends upon which cartridge you're loading. A lot of what goes on in BR and other match shooting is monkey see monkey do. After a certain shooter showed up at a match with a tuner on his rail gun, there was a rash of tuner sales. Turns out he'd only brought that rifle because his fav gun was being rebarreled and he'd borrowed that one. I'm not really any different. I tried some Vihtavuori powders and they worked fine, but really no better than my usual Hodgons. I didn't pay much more for it than the Hodgon, and I've not heard any comments from other BR shooters I know here that use it about $$$$, only from people on the internet.
There are some people here shooting very good aggs with RL-15 and IMR 4350 or even W760. If memory serves, a couple of world records in 1000 yard competition were set this past summer using components not widely touted as "match" or "BR" grade, including powders. Another thing to consider is that smokeless powder performs so well as a propellant because of the way it burns under pressure. A powder like H335 in a BR rifle which is able to handle the higher pressures of jam seated max capacity loads is not going to perform in the same way in an AR-15 or a factory bolt gun that you cannot begin to develop the same pressures.
The best powder is the one that works best for you in your rifle(s) for your application(s). You might use H335 for a small bore 600 yard match load and RL-15 for the same caliber in a plinking or 100 yard match load over a variety of calibers.
Some sites of interest if you are really thinking about BR shooting:
http://www.6mmbr.com/index.html
http://www.sinclairintl.com/
http://www.benchrest.com/
http://nbrsa.benchrest.com/