I've done a good Fairy-free mileage on canal paths and glass-strewn urban roads with 700 x 35c Schwalbe Delta Cruiser+ fitted to my Pioneer Hybrid, which have Level 5 protection the same as Marathon Greenguards. I've got 700 x 28c Marathon on my old Dawes road bike but haven't done enough mileage to draw any meaningful conclusion. They are Fairy-free so far though. Marathons should wear longer, but if you tend to destroy tyres with glass slashes before ever wearing them out, it's better to destroy a £12 DC+ rather than a £20 Marathon (at typical
CRC prices)
I've got some retro-fit Chinese tyre liners from
eBay on order that work out at less than £4 per bike and I'll be fitting these inside some ratty old unprotected tyres used on my hack bikes first to assess their effectiveness. If they do repel The Fairy, I'm even toying with the idea of fitting them inside my Schwalbes for additional protection! Did I mention I
really don't like getting punctures?