"Tiger" haute in die Tasten:
From what I've heard, the 7 speed gearbox is capable to make a downshift over two gears at once, while a 5 speed gearbox can only do a downshift by one gear at a time. So downshifts by several gears can take a little bit longer with a 5 speed than with a 7 speed.
This shift speed advantage may not be necessary with cars with really big engines, as they have enough power to handle almost any driving situation with a one gear downshift. Shifting down further (with full throttle) may only wake up the traction control, if you have 500 HP under the bonnet;-)
Frank