trail centres DO get muddy, they also vary in degrees of hardness.
Also, depends on how well you know 'that' trail centre is how difficult it is. Glentress for instance to most people is known as a 'scaletrix' track, but if you know it well enough you can actually ride alot of
trails not known to the masses therefore requiring more specific tyres.
for instance, if i was to stick to the red trail i'd porb stick to fast rolling, low grip tyres like racing ralphs, nobby nics or panaracer fire or cinders, prob sticking a slightly grippier tyre on the front with both tyres prob a 2.1, or 2.25 max.
Now if i was to do the black or alot of the 'hidden' trails it'd keep a fast rolling rear tyre on like a saguaro geax or nevegal on with a grippier tyre up front, poss a high roller (its what i like) and prob in 2.25 – 2.35 size, tyres with bigger volume and better puncture protection.
Hope this helps better.
Oh, stay clear of conti vert pro's if you value your life