Dura Ace are very high quality, Dura Ace is shimano's top of the line stuff. Not that they really have anything else for track these days, but not for nothing do they call it that. Also +1 on new surly being way, way better and on par with Dura Ace, old surly was about as hard as a donut and nearly as round.

Don't overlook the Milwaukee cogs available from Ben's Cycles. I have one and it's very good. Also is the cheapest non-stamped cog that I know of.

I always consider the number of skid patches in choosing gearing. Another factor to consider is the even versus odd number of teeth. Sheldon Brown says you can extend the life of your chain and cog combination by using an even number of teeth on both the cog and chainring.

http://sheldonbrown.com/chain-life.html

The idea is that each cog tooth interfaces with only chain links in the outer plate or inner plate section of a link. I believe Sheldon is correct, but I choose to use an odd number of teeth for either the cog or the chainring anyway. My reason is that I know I am not diligent enough to maintain a consistent phase relationship of the cog and chain during maintenance activities. I prefer even wear on all the cog teeth at the expense of shorter cog life.

^^ Plus even-even ratios are almost always abysmal for skidding, and bad (9 patches, unless i overlooked something) at best.

I like my 47t chainring; with 17, 18, 19t cogs i have 65, 69, and 73 inch gears available, all with very good skidding capabilities (17, 18, 19 patches respectively, * 2 when skipped ambidextrously) because 47 is prime and odd.

PS: I ride new surly cogs and haven't been able to dent em yet. they seem to be mighty good.