I found the Laggan black a significant step up in technical difficulty from the Laggan red. The black seems to me more like a series of technical features with some trail linking them rather than a trail that contains technical features. The features are generally rocky and steppy, often steep too.
If you're into it the black is very enjoyable and rewarding. If you're not into it it is pretty easy to get demoralised as there's not much to it except the technical bits. The first time I went I managed the first few technical bits but my confidence was increasingly drained and by the end I was miserable and giving up and walking features before I'd given them a chance. On the other hand the last time I was there I thought it was great and I enjoyed tackling the challenges.
One thing I think is to not feel rushed. The first time we were there I felt very much at the back of the group and that I was holding people up, which meant my confidence dropped further each time I messed up a bit.