There are advantages for both Offshore Snap Weights, XPS Keel Weights and I use each about 50% of the time.
For Snap Weights the big advantage is that you can let out any length leader you want before attaching the Snap Weight. If find this particularly useful in clear water. I can remember one bite up on Saginaw Bay (out beyond the Charities) where you needed to have a 150 leader to get the fish to bite – but that is what they wanted.
As mentioned above, the other thing Off Shore Tackle Snap Weights and the longer leader will do is to smooth out the action of the spinner. Sometimes I think walleyes want a nice steady moving spinner so they can locate and intercept it more easily.
A XPS Keel Weight is an in-line weight. It is attached right to your reel’s line with about a 4 foot snell back to the spinner. First of all I think it is important that if you are using an in-line weight you should make it an attractor. What we did with the XPS weights is to make them holographic. I think by having the weight and spinner in close proximity it starts to make the setup look like a school of baitfish – a good thing.
As mentioned the XPS weights are a little easier to fish. Just put them out and attach the board. When you get a fish, detach the board and fight the fish in right behind the weight.
Last, there are times – I think – when the undulating action of the weight, rising and falling from the surging of the boards in waves, actually triggers bites. With the short snell behind the weight, when the weight pulls forward, the spinner surges. When the weight pauses, the spinner pauses and flutters down (maybe looking wounded).
You mentioned lead core – and I have tried it several times with spinner with no luck. I think it might have to do with the lead core line being in the same site plane as the spinner (the spinner does not dive below the lead like a crank bait does).
So, when I spinner fish, I use 1/2 Snap Weights and 1/2 XPS Keel weights and then let the walleyes tell me which is better for the day.