It really is a case of what you are gaining. If you have not tried biwiring yet you arent missing anything. The effect of biwiring on your speakers in your system only has as much value as you place on it. I know a lot of people who did not like the result that came of biwiring their biwirable speakers-did not like having to run extra wire or the sound quality that resulted. I know a few people who own B&W speakers-as I do,who felt biwiring made their speaker sound over blown.I definately feel my speakers-B&W 602s2 and cdm1 nts, benefit from the additional wire. In both instances they sounded smoother and more detailed, as well as gaining a greater presence that was not apparent before.
I am inclined to think it is a synergy issue. Biwiring aside, you first have to figure out what cable is going to work with your system. Then it might pay dividends to experiment. Also, Shorter is better, but I think it will pay to be realistic. Some speakers need space, and a longer run of speaker cable with offer a greater level of flexability. If your speakers are anywhere as placement sensitive as mine you will appreciate the extra length of cable.In the end, You may want to experiment with speaker placement and different cables before you make your purchase,and by then you will likely know whether you want to go the biwire route.