I've had both and they each have their pros and cons.
The 1600B does not do angle compensation below 100 yards, whereas the 1000R does.
I don't remember the specs right now but the 1600B will do angle compensation further than the 1000R.
I also believe the 1600B uses a more complex equation to calculate the actual shooting distance (temp, baro, humidity, angle, and the selected curve) and the 1000R is more basic (angle). Which may leave more room for error at long range.
I bought the 1600B to shoot long ranges, which is fun at the range but my actual hunting ranges are much shorter than my practice ranges, plus I archery hunt as well...so I sold the 1600B, bought the 1000R, and put the extra $ towards more gear.
If you're really looking into a long range range finder look at the gunwerks.
I've never regretted my choice.