Brix/Specific Gravity Refractometer w/ATC

After reading reviews on this gizmo from Northern Brewer, I got the impression that this does not do very well for measuring final gravity. There was a reference link to some convoluted logarithmic formula for calculating the inherent error of a refractometer. Am I better off with a floating glass hydrometer?

I use them both. I use my refractomter for all brewday readings. It's great for taking preboil and postboil readings, which allows you to adjust your recipe and hop on the fly, dillute to proper graivties, etc (All the minute adjustments that makes for great beer.)

And to take my OG before yeast pitch.

After that I use my hydrometer.

The think about suing the hydrometer is you also get to taste the samples.

To me, they're bot equally invaluable.

+1