Its a tricky one, the safety of a fixed income at a guaranteed place of work is nice and safe but its not going to earn you the big bucks unless you own the place.
The contracting is bigger risk but bigger rewards.
I've got friends who have moved into contracting for the money then others who have moved out of contracting because they never felt any ownership sense of pride for the work or projects they undertook as its a mentality of get one job done move to the next. Some have left for this, some wanted more security. Others stay because they love the cash.
I guess if i was in your boat i'd make a list of pros and cons. see which wins. Then consider the risks more, is this likely to be a one off job, what if no subsequent contracts come through, could i easily get a permanent job again. If you can take the risk and have a back up plan if it goes wrong in the worsst case scenario then you have at least prepared yourself.
Saying all that im a firm believer in the fact that you only get one shot in this life so don't waste it, if an opportunity comes up you should take it (addmittedly difficult if you have other responsibilities and ties). If you dont you may alwasy look back and wonder what if.... and thats never fun.
7 years ago i had to make a similar ish decision but the other way around. I was in a well paid job but hated it. I really wanted to change but risked giving up a fantastic career, great money but hating what i did. I saw an old chap sat on the tube who was looking at me and i thought, if that was me in the future looking back at me now would i think " i wish i had done something different". So i did, i quit my job and went back to uni to start again and do something i really liked.
Yes it wasnt fun having no money for a while, and all my friends continued to progress and buy nice houses, cars etc but in all honesty it was the best decision i've ever made. It was a risk but it paid off and now i love what i do.
You only live once, dont waste it i say.