I usually use a nail knot covered with PlioBond/ZapAGap. I have used a loop/loop connection, I have used a piece of mono to the fly line & loop/loop to leader...
I find the loop/loop & knots (not zapagapped) get hung up in the guides.
I fish dry flies with long leaders (10+ feet) & when brining in a fish, changing flies, pulling in line to move to a new spot, the line hangs in the small guides (I fish most 4 weights & occasionally 3 weights).
so, & I do not consider myself an expert either, but I do know what I like... the smoother the connection the better! nail knot/pliobond...done.
later,
An Oregonian