I’ll be the outlier. Don’t buy either one yet. Invest in some great testing gear (Hanna, etc) buy your emergency spare parts (heater, pump), and take time getting to know your tank and what it needs (do you have a doser or replace filter socks with a roller system?). I’ve had my tank about a year and still test manually every three days. Just installed an Apex after spending a couple of months reviewing Apex and GHL. It’s a “nice to have” but certainly not a “must have”.