Level loop vs multi-level loop
Level loop is uniform and the most durable — it is what commercial specifiers use. Multi-level loop introduces pattern and softness by varying loop height, at some cost to how well it recovers from heavy furniture.
For a Fife home with a mix of family traffic and a desire for something more designed than a plain twist, a subtle multi-level loop in a heather colourway is usually the sweet spot.
The snagging question
A pulled loop leaves a run that is visible and annoying, and it happens with cat claws, pet nails and, occasionally, a rough vacuum bar. If you have cats, choose a cut pile.
If a loop does pull, do not pull it further — trim it flush with sharp scissors and it usually disappears.