Just had a chance to use them both in the same afternoon with basically same conditions (15-17 knots).
I have had Fuel 2002 for a year, just rigged up 2003 for the first time (brand new). The size is comparable.
-The leading edge can be pumped up quicker on 2003 model, although it does not seem the tube would be smaller in diameter. They have, however, NOT added the "air stopping" balls in the smaller struts (naish style), so it is still somehown annoying tu pump it up alone
-Better build, more reinforcements, black color rocks
-Had a 2002 bar on both, lines and safety leash - so cannot comment on this part
-Did not get a feeling that it is really much faster turning than 2002 model, although this might be due to my attachement point settings. I followed JohNny TBKS advice (I think it was him) from this forum, wherE he suggests putting leading lines to the 3rd position (farest away from the leading edge) and rear lines to the farest away position from the trailing edge. The turning speed might change if I would put rear lines to the closest setting to the trailer edge.
-2003 has just so much more lift and hanging capabilities. I could not believe my eyes: with the same move, same tehnique, I could stay up there in the air for substantialy longer. Additionaly, with 2002 I was comming down rather fast - with 2003, it was softer and smoother. Cannot explain why...
-2003 goes into the end of the window much quicker and basically without doing anything special with the kite - it just goes in front of you. Nice for holding it up in higher winds (less power) and helps you edging at the same time. I was even annoyed sometimes in around 15 knots wind, since i had to power it up time to time to get it more back into the window to get more power out of it.
-After a few crashes, using the same tehnique, I got a feeling 2002 Fuel gets water relaunched easier. It might just be the fact, that i know how to do it with 2002 blindly (did it so many times while learning ).
-2003 had a very very rigid style of hanging up there - no jellyfishing at all. 2002 does it ocasionally. Anyhow, as far as i can remeber, jellyfishing does not affect performance - it does however give you a better riding experiance if the kite does not jump around the sky that much.
-Cannot compare power/depower range, since my 2002 Fuel has been rearanged in teh sense I put new strap on with longer power/depower possibilities.
-Can it be for 2003 model to have less aspect ratio?? Did not check the actual data, but it sure looked to me once in the air.
Overall, I like both kites. Anyway, juts my first feeling is that Slingshot made some progess in the new model, especially in flying capabilities (more stable) and unbelivable better hangtime.