E-600 vs E-420

I'm eying a used E-600 here in Germany - for a friend whose (non-Olympus) DSLR died recently. While the offer sounds good, two questions remain - maybe an E-600 user can help?

a) According to the specs here on dpreview, the E-600 is a downspec'd version of the E-620, marketed in North America only. However, this E-600 comes with a German manual, so it seems this version has been sold in Europe as well?

b) I own and like to use my E-420 (that's why I recommended the E-600 to my friend in the first place). As I might have the choice - is the E-600 an improvent over the E-420, image stabilisation aside? Especially IQ-wise?