Should I replace my 10000km Schwalbe Marathon Plus Tour with a 2000km Schwalbe Marathon Winter Plus?
I don't think the holes in the winter tyres will be prone to punctures without the spikes in them. They're a very small target. I have had damage from the inner end of the spikes themselves wearing through the belt on tarmac (occasionally icy).
These winter tyres aren't as tough as the marathon plus (tour) though, both in terms of overall puncture protection and wear - winter compounds are softer. They still probably have more life than marathon plus with 10000km on; at least at the back that's about how much I get.