A Split panel, is like two small panels joined together and then paralleled together. This way, half the current flows through each half panel. Less current is less heat, and more efficiency. Also, your system is less susceptible to shade power loss.
A Perc Panel (Passivated Emitter and Rear Cell) is the latest advance in technology (invented in Australia) and is basically a more efficient panel. The key is the “Rear Cell”- it slows for light to hit the silicon on the way in, and on the way out of the panel.