I have ridden Glentress, Innerleithan and Dalbeatie as well as Laggan.
My take on it.
Glentress – fantastic facility with a bit of everything for everyone and so well laid out that you get great value descending for the amount of climbing you do. Great cafe as well. Love some of the blue sections, find the (red) climb a challenge but achievable. Getting the tandem round all the hairpins is a real challenge. One day we will clean the whole lot. Has the only jump I have been able to get the tandem airborne at. Lots of variety from smooth flowing blues to tricky blacks
Innerleithan I just did not like but I have not been there recently. I thought you did an awful lot of climbing for your descending and I found it very artificial feeling. Almost as if the builders went ” this bits dull so we will stick a pile of boulders on it” Some great sections however and I believe there is a new bit put in that might improve it for me. Just not the “value for climbing” of GT
Dalbeatie. Some of it I loved – and I like the undulating nature rather than big climb/ big descent. An early rocky section caused us a nasty fall on the tandem as we bridged which took a while to get the flow back and the fear away. Seemed to start off hard and get easier.
Laggan – love the more natural feel of it and the use of natural rock. Black truly worthy of its status. Big rocks beside the bottom of the descent scare the crap out of me. Nice for mixed groups as the loops are short so you can keep meeting up at the cafe. Best views of any of the trail centres I have ridden. almost feels like the real thing 🙂
Its very much a horses for courses thing. I think overall GT is my favourite as it has so much to offer anyone of any standard. You can have a nice gently day or an almost full on gnarl depending on your mood
* note this is just an opinion*