Coiling the cable makes it a crude inductor. If it's a well shielded cable, it's probably less of an issue, but it's one of those audiophile no-nos.
I use Transparent Super cables of differing lengths...I've been told the networks "tune" the resistence, capacitance and inductance of the cable to be identical regardless of cable length, and I sure don't note any problems. I'd be inclined to use the two different lengths....just try not to obsess about it.