To ME and My way of thinking;
The one on the left is showing a Richer than need amount of gas. The one on the right MAY tell me rich and maybe a little soot deposit from Oil burning.
I like the older bikes to show a Light Tan and NO black..
How dark are the muffler ends? IF black normal but IF sooty Black, Too much Fuel (rich) and or Oil getting burned.
Does your bike Use any amount of oil that you notice?
The plugs look too well used.
Might think about NEW set OF Stock HD ones.
Could make a world of good in the runability of your bike.
As fin would say "use a little copper grease on the threads" when you install the new ones.
In the USA, Plugs for harleys are about the best buy Yet.. Under 5$ US for 6R12's set and that is from the Harley Dealer..
SHhhhhh don't let them know they are considered
Cheap here in the US or they will Raise the $$$$.
signed....BUBBIE