Which solar water pump is the best?

It depends on what you want to use them for. Solar water pump types range from submersible pumps and surface pumps to booster pumps and sewage pumps. Each type has peculiar features; hence, you might need more than two options to settle the matter economically. Low-cost plastic or stainless pumps have a short lifespan and their motors are generally weak for low and high-demand applications. You will also find that cheap pumps often lose wires, leak and most likely don't contain any parts.