I flew OTP-IST-LAX and return several times in last 10 months, but in Y+ or C. With exception of IST-LAX, the flights leave on-time and arrive early. IST-LAX tends to always leave 30-90 minutes late, but always make it earlier or on-time to LAX. It is because of all connecting pax.
C and Y tend to be full, but Y+ is only full after cash upgrades. Given the 1/3 chance of getting free WiFi, great food (compared to other airlines) and great lounge in IST, I would choose TK.