Stay on Fresha if you’re solo, doing fewer than 50 bookings/month, and you actually use the marketplace discovery to find new clients.
Switch to custom if you have 2+ practitioners, 200+ bookings/month, an existing website, or you’ve done the math and the 20% new-client commission is bleeding you. A $12K custom build typically pays back in 8–17 months at that stage and is fee-free forever after.
Don’t switch yet if you don’t have a website at all and don’t want one — though most clinics building a custom booking engine ship the website at the same time.