The alteration in sailplan for the Tornado in 2000 was a larger square top mainsail, spi and a jib with longer luff. I dont think the 'new' Tornado jib is much larger than the old one. One interesting thing they found during the test event at Quiberon was that the old-rig Tornado was faster upwind than the "new" rig. Even with the added power of larger sailarea and double trapeze, the old rig was very effecient, well known and did not have the extra weight/drag the spi-gear added. So if your Tornado friends say that their upwind performance has improved hugely with the new rig, something must either have been wrong with their old setup, or the new-rig saildesigns have improved since the test event (which is very possible).
A longer luff (and aspect ratio) is more effecient then a shorter luff, which means better speed in most conditions. When overpowered and especially on a reach, a shorter luff but more area (lower aspect ratio) can be faster.
If I could choose, I would choose high-aspect ratio any day, as you can then install a selftacker. A selftacking jib makes all the difference upwind singlehanded (not legal when racing F-16) and downwind under spi in any configuration.

For more information about the ISAF evaluation event, which is good reading: http://old.cruisingworld.com/2000/03/isaf1.html