The 'benefit' of fitting the Smartmods leads are :-
1/ they are of far better quality that the original
2/ the engine to chassis earth lead is sheathed, unlike the
original which usually isn't and therefore 'open to the
elements' ie, corrosion and therefore power loss.
3/ they carry the 'load' far better than the original.
A good example of bad/poor earthing is a car's lights....and we've
all seen brake lights flashing with indicators etc on many cars....
and flickering headlights. Most electrical faults are through bad
earth connections, so fitting these is a good precautionary measure.
But having said that, most owners will not detect much if any change
when fitted, but....some owners have noticed an improvement in
engine response due to better conductivity and better spark/fuel burn.
They will without doubt be a benefit if you fit a more powerful ICE
system.
I think it's a shame they don't do them for the CDI, as I would
have a set immediately.(it appears they've never had an orginal
set to use as a template...)