Both are rated at 2000 watts but the pure sine wave output of the MS will result in better performance as though it has more wattage output in many cicumstances. The cost difference is why the mfg. does not want to "just do it under waranty". It is not hard to change out by one that is accustomed to working with electrical circuits. Good luck and keep us posted on the decesion and results.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7