Trout flies fall into two categories - attractors and imitations. Strangely an exact copy seems to be less effective than a ragged one. The best flies seem to hint at their ancestry. For example there are some wonderful stonefly imitations, but the good old stick fly does just as well. Many rainbow trout fishermen are brought up on lures and wonder why they are not so effective for brownies.
Brown trout are far less aggressive than bows.
They are less likely to take a lure. Most anglers therefore rely on imitative patterns. Those lures which do work for brownies tend to look like fish and thus fall into both camps. The only time when you can really catch brownies on lures is at the beginning of the season when they are really hungry. It encapsulates the best approach to brownie fishing.