I reckon dunlop 756 is still the go if you can get them. I think they have been replaced by the geomax now. I have used the geomax as well. It is far better grip than the 756 when new. Looses it edge quickly though I found. Say less than 300km. Once this happens they shed knobs badly and the great grip you had when new quickly turns to not sure and/or I’m praying it will grip. The 756 probably doesn’t last any longer but they don’t shed knobs and are relatively consistent through the wearing process.
At the end of the day it is all personal preference. In general it comes back to what you need/want. Tyres that grip really well don’t tend to last and tyres that last don’t tend to grip. My personal vote goes for grip over lasting. At the end of the day there doesn’t really seem to be that much difference in how long any of the tyres I’ve tried have lasted anyway.
Haven’t tried any hard terrain tyres though.
I’m lucky to get much more than 500km out of a tyre I reckon. Had my bike 2 years, done 4100km (had 7 months off with broken wrist in that time), so 7 rears and a few less fronts in two years. So just over $700 a year on tyres. Worth it I say.