I would rather consider repairing the old one, or at least trying to find out what's wrong. That sounds like a heat issue maybe. No guarantee left? Customer support? I mean a new one is surely more expansive and the old one doesn't seem to be THAT old, looking on the components.
As for the performance, lower screen resolution means less work for the GPU and that Samsung one seems to have a better GPU and CPU, anyway. Seems like Performance gain inc if you get the new one ...