A corollary to Kijanki's good comment is that if the longer cable behaves in a neutral manner in a given system (which is dependent on the impedance characteristics of the speaker as well as on the cable characteristics), the shorter one will too!
One thing is for sure, IMO. Timing differences, which were asked about in the OP, won't matter. Electrical signals propagate through wires at a large fraction of the speed of light in a vacuum (186,000 miles per second) at treble frequencies and higher, and even the slowest propagating audible frequency (20Hz) propagates at more than 3000 miles per second. Since 3000 miles/sec is roughly 15000 times faster than the speed of sound in air, the arrival time difference at the listener's ears resulting from a 10 foot difference in cable length would be the same as the difference that would result from his or her head being 10/15000 = 0.0006 feet closer to one speaker than to the other (and far less than that at mid and treble frequencies). In other words, not likely to be audible!
Regards,
-- Al
