You are really not getting any additional value in the SBE3 over the M2. The price difference is quite drastic, but the features are just not there.
The SBE3 looks cooler and slicker, but I don't think it's worth the extra $400ish.
If I was debating between the 2 for a dedicated turkey gun, the M2 would win for me. You have a 24" barrel option and a compact stock option with the M2 that is not available in the SBE3. For a duck gun, both do well with a full stock and long barrel.