I don't see any major difference in the two. My refract. was only $45 at drsfostersmith.com - the 'generic' Premium Blue refract.
Really, there's only one option: built-in light, or not. I use the PC
bulbs over the SW
tank to light the prizm.
I don't like hydrometers. They are too easily skewed by tiny air bubbles stuck to the glass, and are calibrated for 65 degrees F so you have to adjust for the typical 10-15 degree increase in the tank's water temp.