The Catamount is the shoe Brooks builds for going hard on rough ground, and the 4 runs a reworked SkyVault plate over nitrogen-infused DNA Flash v2 cushioning. At 269 g it is light enough to race on, and the plate is what keeps it climbing when the gradient turns steep and your legs stop wanting to.
It suits you if you enter trail races and want one pair for the hard days around them — the steep climbs, the technical descents, and the tempo efforts you do to get ready for both. It carries far enough to hold up over an ultra distance.
It is not a cruiser. The cushioning is responsive rather than deep, the plate keeps the ride firm on a slow hour, and the fit is snug the way a race shoe is snug. Nothing about it rewards plodding.