Use a snap absolutely. What will happen if you don't have a snap is that the line will get off to one side of the line tie and cause the bait to run a little crooked occasionally. I also feel that a knot tied around the eye of the bait is not going to be as strong as a knot tied around a thinner piece of metal.

I wouldn't worry about a groove in the eye or whatever. I have baits that must have about 100,000 casts on them and there's no problem with a groove in the eye or anything. I personally believe that once your bait gets worn in a little and the paint gets rubbed off the eye, the joint, and the hook eyes, the bait makes a little more of a high pitched squeak which I think is good.

good luck and enjoy