The "early" Woodstocks (21, 22, 25, 25C) have only slightly improved accuracy over the Classics.

The biggest improvements in the math algorithms are the ones found in the 27, 19C/29C, and 67/97. I'm not sure whether the 91 and 92 use these algorithms or the older ones.

Some minor further improvements were made in the 30-series, 41, and 10-series, all of which use essentially the same algorithms.

The math algorithms got a rewrite for the 71B computer using Saturn, to be compliant with the IEEE 854 radix-independent floating point standard. These routines, minus some of the IEEE features, were used in all of the Saturn-based or Saturn-emulating calculators (clamshell, Pioneer, and graphing).