The magazine Obligement published today a comparative about performances between AmigaOS 4.1 and MorphOS 2.3 on Pegasos II.
This comparative is based on 20 groups of benchmarks including boot time, processor, 3D, USB, IDE hard disk, WarpOS emulation, emulation 68k, etc.
No subjective comparison was made, all benchmarks are based on numbers.
The article is in french but very easy to understand, and it's available on
http://obligement.free.fr/articles/amigaos41_vs_morphos23.php