Its a function of cost, power (lumens), and quality. I'd go for the highest quality, most powerful lights you can afford. Look at lumitec or lumishore. Lumitec is a great product at a fairly reasonable price. I really like the Lumitec SeablazeX2. These lights come in full spectrum RGBW and White/Blue. The cost isn't too crazy either. It depends on what you are looking to do with the underwater LED lights. If it is just for the dock or while catting around, go with whatever color floats your boat. If you are fishing the rigs at night for tuna, I prefer blue.
Light with longer wavelengths is absorbed more quickly than that with shorter wavelengths. Because of this, the higher energy light with short wavelengths, such as blue, is able to penetrate more deeply. Then you need to factor in the # of lumens the lights will be producing.