Tires are a trade off between mileage and grip. Me personally, I'd prefer better grip than durability and therefore would choose a softer tyre compound.

If you want a tire to last longer, expect there to be a trade off in the grip department as a more durable tyre will be a harder compound, and will therefore require more heat to get them upto optmium temperature if they ever reach it on the road.

Regards the wear bars, yep the ribs in the centre tread are your wear bars. My fronts have worn on the outside edge more than the centre of the tyre which implies I have an alignment issue, i.e. positive camber as opposed to the more preferred negative camber.