I think we all know what the OP means. He wants to know which trail centre is most like riding a real mountain and it’s a fair question.
Personally I don’t really like trail centres that much, which confuses me as many of the trails are actually great. The natural (non trail centre) riding does it for me as it’s more about adventure and riding stuff not designed for bikes. I think it’s a mindset thing, a feeling of remoteness and being close to nature.
You know what to expect at trail centres but riding in wilder areas can spring up more surprises. Go to Glentress and you know that at some point you’re going to see some bell end do a bunny hop or something in the car park then look around to see how many people saw his amazing skills.
Kirroughtree black is probably the closest thing to a mountain I’ve ridden at a trail centre. I’d still much rather ride my local trails though even if they are a bit thin on the ground and limited at times.