Straps are better at conducting current in this application because they last longer than the equivalently priced cable assembly that would otherwise be used.
The only significant impediment to current in that ground strap or wire would be resistance at the connection points, or resistance as a result of insufficient conductor size. Remember, the oxidized magnesium tranny housing, and the rusting steel screw on the chassis are part of the circuit too. There's no leakage, loops, shielding, HF, RFI or other issues here, and older cars probably arent all that sensitive to higher impedence paths to ground anyway. The 914 isn't exactly high tech - an appropriately sized wire in good repair would work just fine.
Most constructions of copper braid are extremely flexible when compared to stranded wire of a given 'circular mil area' (conductor size) and braid is generally tin plated so it won't readily corrode. (corrosion equals resistance)
For reliability in high flex applications, fine conductor stranding and insulations that not only resist the stuff found in automotive applications but also survive at high and remain flexible at low ambient temps are essential -Insulated wire that would perform as well as braid in this application would be expensive. You'd be paying for fancy insulation just to keep the strands bunched.
You will notice that another major grounding path - the ground wire from most battery posts to the chassis - is just that, yer basic dirt cheap automotive wire. No real vibration there and little heat.
IIRC, the 914 ground strap doesn't even have terminals - it is just tin dipped and punched. Cheap, simple, and reliable.
Jeez, did I just write all that about wire...
------------------
-- Dave
Pics of my '73 project here: [URL=http://members.tripod.com/mike4g/dds73_b4pics.htm]
[This message has been edited by DDS (edited 07-21-2001).]