What fun! Really!
I always enjoy planning my wire runs on the bikes, trying my best to balance electrical and mechanical functionality with aesthetics. It can make for some challenging choices.
I usually go with B&M dual-conductor ("zip" wire) simply because it is of generally good quality with a reasonably durable sheath of even thickness. It is also small, so it can be routed easily.
That said, it (like most similar wire) can be subject to compression by cable ties if one is too enthusiastic in tightening them.
For that reason, coaxial cable may be ultimately linger-lived, as it has the "hot" lead in the center, with the ground return lead in the form or a woven sheath beneath the top layer of insulation. Of course, on an alternator it makes no difference which lead is connected where, but it doesn't hurt to adhere to convention. The trick with coax is to strip it properly for a good result at the connector. The center lead will always be longer, because the outer weave must be separated, then twisted and tinned with a soldering iron to make a durable connection point. The result is the two leads are usually separated by about 15mm or so, but this can work nicely for spanning the distance between connection points on a dynohub. Just be sure to shield the outer lead with heat-shrink tubing, then sleeve a larger diameter piece over the whole coax so the weave doesn't separate.
While arguably more durable, the coax is larger in diameter, which can be problematic on installations where it is desirable to route the wiring inside the frame, fork and chainstays.
In the end, either lead type -- two-conductor strip wire or coax-- will do the job. Looking forward to photos of your final installation.
As a data point, my Dean's connectors have remained clean and secure at the point of connection and completely failure free after nearly five years' use, so encouraging in terms of durability and reliability.
All best luck,
Dan.
