OK, I'm going to reply to my own question, so other readers can use it if they like. I bought the prophet XL eventhough a lot of people told me it was no workingstation. That is correct. It is not. But in that respect, neither is a Nord Stage (which I also have). After playbing with it for a whole week almost everyday, I do not regret the purchase. With the digital oscillators all synth bread and butter sounds are easily created (synth brass, strings, leads,...). I have programmed (nothing fancy) a few 32 voice piano's, rhodes,wurly and clav sounds. I have not come accross note stealing. So polyphony is good (i do se the sustain pedal). There are also a few pop brass patches (brass with synth brass) which are very usable in a live band. Not the most authentic acoustic pop brass, but it cuts through the mix.
I'm goign to buy the sample robot stuff so I can sample some brighter pop strings and brass sounds for live use. And maybe add some dx-type of e-piano sounds, but with 50Gb of room, that should be easy.
I also heard the 8dio was going to launch acoustic sample sets, now that all the synth stuff is finished. So maybe that's promising too.
All in all I'm blown away by the sound quality of this beast. It's expensive, but so is a nord stage. For me it's bread and butter sounds are super. So if you don't need accordeons, which you also could sample) it's got most of it inside. The piano's are more ballad, chill, cinematic than bright rock piano's and the hammond is not as flexible as the nord. I have used a neo vent with the basic hammond sound of the prophet and it does sound very capable when you don't need to many variations in your song.
So for what's it worth. I like my purchase and it also has allowed me to do the more cinematic ambient stuff as well. I'm going to buy me a modal argon8 as well to use it together with the prophet. I think this will be a very good combo.