I used the Schwalbe Marathon Plus MTB for about a year and a half without any punctures, these were fitted after green gloopy tube stuff totally failed to seal tiny flint hole. Riding on mixture of surfaces, trails on chalk and flint, roads and canal paths with usual canal path sharps! Only criticism was that on wet roads they didn't inspire confidence, quite hard rubber therefore hardwearing, I guess. Strangely, as the tread wore the grip on roads seems to improve.
Marathon Plus MTB are only available up to 2.10, so look quite narrow on an off road bike.
When I got the KTM, the OEM tyres are quite light build so fitted Smart Sam Pluses, 2.25, I confess, with aesthetics in mind, they do look better on the bike, maybe not as bullet proof as the Marathon plus, but no punctures yet on same surfaces as before.
Smart Sam + seems a softer compound, as Jackandy has mentioned as well, wear rate seems a bit quicker, but that seems to be the trade-off for better grip on the road.
In short, very pleased with the Smart Sam + on and off road.