Bicycle Mechanics - Difference between Ultegra 6603 & 6604-G cranksets

I was checking them out on Colorado Cyclist: http://tinyurl.com/6yqbze

Nothing more that a weight difference and finish, right?

Is the 6604 compatible with an Ultegra 6600 BB?

Also, this is for a hill climb bike project and I intend to run just a 24t up front with regular 10-spd in the rear. I assume a typical short-cage 10spd Dura-Ace derailleur will be fine?

Thanks in advance,
-Steve

I believe the 6604-G is a part of the relatively new Ultegra SL line--a half-step up from Ultegra to Dura Ace. There's information on bikeforums and elsewhere about how SL compares to regular Ultegra.

As for compatibility, I imagine they are all compatible--though I'm not certain. Look on http://www.shimano.com.

Sounds like you intend to run a triple crankset with just the inner ring at 24T? I'd be concerned about the cross-chaining between the chainring and smaller cogs. I'd be inclined to go for an older system like aquare-taper, ISIS, or Octalink, so you can swap in a longer axle and move the crank out a bit resulting in the chainring better centered relative to the cassette.

Edit: on second thought, the system may be OK. I just checked my road bike with 2-piece triple crank and 10-speed cassette. The inner chainring lines up pretty well with the 4th largest (lowest) cog, so it's not too far off from center and maybe you'll be using the larger cogs more for climbing anyway.

Great, thanks.

I know that a longer-cage rear derailleur would be necessary if all three chainrings would be used, but is it still necessary for a single-ring up front?