Perthshire — sometimes called "big tree country" — sits centrally in Scotland with a genuinely strong Pony Club and riding culture, helped by good land and a position that makes it easy to reach from Edinburgh, Glasgow and the Highlands alike. It is one of the more horse-literate central Scottish counties, with decent facilities and an active local scene.
The county spans lowland river valleys around Perth itself and rises into proper Highland-fringe hill country further north and west, so both gentler family ponies and hardier hill-bred types are genuinely available depending where in the county you look. Its central position is a real practical advantage — a Perthshire viewing rarely means an enormous detour whichever part of Scotland you are searching from.