Purgs are ok as a front tyre, nothing special. Good in the dry, less capable in the wet. They have to be leant over hard when cornering and have a tendency to let go without warning. On the rear they feel like pedalling through treacle though.
A Specialized Butcher makes a much better front for sheer grip without that much of a penalty on rolling resistance IMO.
Ground Controls are a decent choice for all round use on the rear, as well as being quite grippy in the dry up front.
For trail centres I like to run a GC 2.1 on the rear and a 2.3 Butcher up front. For XC / winter road and bridleway mile munching the GC goes on the front and I put a 2.0 Fast Trak on the rear.
The Grid casing makes setting up tubeless a bit easier and I’d recommend for anyone riding rocky / flinty trails. Otherwise the Control casings are fine.