Sander,
I can comment on a few of your questions.
The Roland VA3,5 and 7 can all record user styles.
The Rolands can also play songs, show lyrics and choose the next one to play while the current one is playing. Than, when the song is over, the next song is ready to play.
The Roland can also play styles direct from disk which is something the WK8se can't do. The WK8 makes you load the styles into the internal memory before you can play one.
Roland has more than the 4 variations. There are 4 different size bands and each band has 2 variations for a total of 8 variations in all.
The Roland's sounds are in my opinion much better than the Generalmusic. I especially like the fact that the VA7 and VA5 have 128 note polyphony compared to the WK8's 64 notes. Also, the roland has I beleive 64MB of sample Rom which is much more than the WK8se so the sounds are much richer and more realistic. Also, if Drums are important to you, no comparison here either. The Roland drums in the new map are incredible. Did you know that there are 4 maps of sounds in the VA series. Map 1 are Sound Canvas, Map 2 are from the G800, Map 3 are from the G1000/EM2000 and map 4 are the new sounds. Over 3600 in all.
The WK8 does has volume fader controls which are really handy and has a really good sequencer, but so does the roland, however, the WK8 sequencer has the edge on the internal sequencer. Also, it has a lot more memory than the Roland.
Good Luck in your Choices,
George Kaye
Kaye's Music Scene