Monos

272.66 fixes the premature float bug. In some cases, this might be reason  enough to choose it all by itself.
The only other change is that the threshold to skip the "race to the bottom" code (which leads to being stuck at 90 V on the panels) is reduced from 0.50 A to 0.05 A. This is usually enough to provide a noticeable improvement in PV production, especially in cloudy or rainy weather when you really could use every joule of energy you can get.
In all my patched firmware update files, there is a .txt or more recently a .asm file that has comments on what it changes. As an example, dsp_272.66_patched_05.asm starts with:
Edit: As for which one is "better", it's a user preference. The patched files are all amateur experiments, but sadly, they tend to perform better than the factory firmware.