I like both but I need to know in advance to psyche myself up and bring the correct bike. I no longer favour long epics because my ME currently can leave me totally destroyed sometimes before the ride ends. Trail centres tend to circuit a central point that can be returned to quickly should you need to cut short your ride. Back country stuff needs clearly worked out bailouts or your stuck.
Just getting older and less fit with a possible degradation of confidence I'm afraid.
EDIT:
Just read and watched various bits about Lairig Ghru. Looks too tough for me, lots of cross drains and rocks, reports of boulder fields and bogs, mention of a fair bit of pushing and carrying with the odd burn to ford. Aviemore last time and Torridon although in spectacular scenery pretty much killed me and in such scenery I nearly always crash. Nope Not for me.
I in no way wish to be the reason the rest of you dont attempt it so dont give the idea up because of me. Just tell me if the chances are you are going to try it so I can save my pennies and not get a train ticket.