This sounded interesting, so I googled for some benchmark test to measure differences. I found nbench, which measures performance by executing some typical algorithms and compares them to a Pentium 90 based system. So I installed it and run on the i586 CHOST system, then rebuild it completely to i486 CHOST and run it again. The differences are not that huge, but on some algorithms they’re measurable:

The first 13 bars are the different algorithms. The main difference is on the string sort, which is heavily memory dependent. That last 3 rows are a index based on the algorithms. Here is main difference on memory index, as the normalized version shows very clear (positive values mean that i486 is faster):

As there is no significant disadvantage of the i486 CHOST, this seems to be the choice.

If anybody has other (free) benchmarks to suggest, please let me know.