Hi
What's the opinion of wearing leathers for off road use are they practical?

Not at all (imho), you will cook on even the coldest day.

They are heavy, not waterproof and you'll bugger them up by getting them covered in sh*t.

You want a strong fabric that can resist tears from bashing through the shrubbery, lots of ventilation and some waterproofing.

I use Sinsalo Enduro pants and an old HG jacket in the winter and MX pants and jersey in the summer.

Depends where you are and what you are doing. Leather tends to survive a few falls, Goretex and fabric is destroyed. Leather rested on the exhaust survives, nylon melts. Leather can be repaired by any cobbler, Goretex and fabric is throw away and includes garbage like glued on plastic zips and velcro with a service life measured in months not years of hard use in a lot of cases. Dust covered nylon doesn't let the Goretex breath so you get wet from the inside or wear a rain suit just like you would with leathers. Fall in a river wearing the full Horrible Gherkin named-after-a-North-African-Tribe set up and once you've taken the various layers out it'll still take a week to dry, just like leather. You can wipe down a pair of leather trousers and wear them in a bar, you look a prat in MX gear. The comfortable temperature difference is in favour of the Goretex, but by how much depends on the wearer. The Goretex is like a big sign round your neck proclaiming you can afford to spend the price of a running bike on your jacket.

For a week in the Alps in May you won't beat the Goretex. If it's January I'll go with anything that lets me get the right kit underneath, in my case cotton treated with waxproofer. To cover every possibility for months on end on a 40 mph bike, I'll mix up armoured jeans, leather trousers, wax cotton etc. to give the most flexible solution.

A one piece race suit belongs on a track, any other use that isn't so single purpose and its compromise time.

Andy