Ideally I would think tying directly to the lure is best.

However it is so convenient to change baits with a snap swivel.

What is the real cost of this convenience with:

Crank Baits
Jerk Baits
Top water baits

I would think trade-off may be different with each application. My theory is there is not that much cost using a snap swivel with a crank bait; but a much greater cost to the other applications due to loss of action of the bait.