Totally agree with you TimTom. I'm lucky in that my local trail is just a mile away so riding on the road for that bit's ok and as soon as I get there if it's really muddy the Trailrakers mean I can get up all the climbs, have plenty of grip in the corners and actually "ride" all the way round instead of getting off and walking!!!
Trail centres are generally different as "most" drain very well so you can use one that gives you the best combination of grip and speed but again you have to try them and find which is best for you. I run Nobby Nics and they're ok but it's a never ending search find the best so good luck.