cable length

OR you could get MUCH better 5 foot cables than the 10 foot ones for the same price.
The other point could be if the cables have a signature coloration that complements your system, or what you like... the length might have an effect on that, or it may not.

I agree with Elizabeth, get the very best you can afford. I would also suggest keep the speaker cables as short as you can get by with. Power cords, again they are by the foot cost, so that must be concidered. If you agree with that power cords can improve your system, than the longest you can afford to maximize the benifit.

Jadem6 is right. Shortest possible speaker cables and longest possible power cables (but there is a point of dimmenshing returns beyond about 6 feet).

Just a question on the same topic. I wonder if it is harder to sell cables under 8 feet? This might be a factor when considering purchases.

Be careful, there is nothing worse than a cable not long enough to reach, some speakers like Thiels need at least 8 feet between them and depending on circumstances maybe 9 to 10 feet. So if you ever change speaks... Also resale is not as good IMHO.