Creation have 2 zirconia porcelains. One is feldspathic and the other is synthetic. I personally didn't notice much difference between them. I probably preferred the look of the feldspathic, but that's very subjective.
Creation is a fantastic porcelain system, however it takes a lot of work to get a great result. It's not the type of porcelain that you can just pick up and get good results straight away. Often due to the high chroma in the ceramic, they tend to come out dense. Therefore it needs ht (neck transl),clear, Incisal, or other translucent powders layered over the whole crown. Then the results are amazing. Ivoclar tend to get really nice results in a much easier way of building u p.
I use VM9 currently and have had no issues with it. I use the internal stains to stain the white non coloured zirconia to the correct base shade. After firing, i do a quick thin base dentinge wash fired over the coping, fire that and then straight to full buildup. I get some really nice results using this technique without the liner material. I have not had any fractures between the coping and veneering porcelain.
I do a lot of shade takes and have found a 50/50 mix of ee1 and enl Incisal matches most of the enamel of light teeth - a1,a2,b1,b2 etc.