I had a ktools site for a year. Pros- if you have php experience, customizing is easy. I had none but managed to figure a lot of stuff out, plus others who had built the site were helpful. Cons - you are entirely on your own when it comes to marketing.
Symbiostock - pros - backlinks from being connected to others help with seo. Wordpress documentation and support is good. Tutorials for setting the site up is getting better. Growing network of people to help with issues. If you have a large portfolio, multiple sites and/or can add more backlinks, seo advantage might work for you. Cons - more difficult to build than ktools for me, despite having prior wordpress knowledge. Documentation - not good for the software. Lots of customization might be required, depending on your design taste, and sometimes its difficult to find answers for your particular problem.
Disclaimer...these observations are based on my experiences. Some people have done well with both ktools and SY. Size of portfolio, software knowledge, and ability to market all play in to the success of a site.