Not optically worse.
CR39 has lower index of refraction (1.498 vs 1.54) and so it is heavier. It has worse chromatic aberration (Abbe 58 vs Trivex 45). So it's really only good for light prescriptions.
Trivex is also easily drillable making rimless easy, rimless->lighter; PC tends to crack easily.
But yes Trivex is a little more expensive than CR39 but in my experience a lot better. If your lenses last 2 years, lenses are not where you should save money.