Funny to find myself agreeing with Joe and not with Ted!
I took a friend's Darne out at Christmas and shot the longest string of misses I can ever remember. I missed ducks, pheasants, woodcock and pigeaons with equal ease. I consider myself reasonably adaptable as I shoot so many guns. I think myself to be of average ability, better on game than clay targets.
With the Darne, I dont think I could have shot myself in the head itf I had put the muzzle in my mouth.
I know some people love them but for the life of me I can't see why. The French should stick to making cheese and eating it while surrendering
The term 'best' is simply shorthand for a gun of the highest quality. Not all London sidelocks are of the highest quality but it takes a good bit of exposure and practice to work out a 'best' quality gun from a second quality one.
Looking at old catalogues by top firms gives some idea of features and pricing differentals.
'Best' guns can be boxlocks (Churchill never really made up his mind if the Smith boxlock 'Hercules' was his 'best' model or his 'Premiere' sidelock, or both).
Of course, 'best' hammer guns were the finest guns made, using the mechanisms available in their day, as indeed were muzzle loaders.
Before the 'stocked to the fences' style came to be universally adopted (around 1900), 'best' sidelocks were made that were not. Consider an early Grant sidelever or a Holland & Holland first model 'Royal' as examples.
Some very embellished guns are not best quality inside - they may have cheap Rogers or Baker locks behind the engraving.
Some makers offered a 'best' sidelock and/or hammer gun and then an 'Exhibition grade' or 'Modele de Luxe', etc as ever higher demand for frills, decoration and finery were made on top of the very finest workmanship, materials and operation.