The most obvious differences are on the type of financing offered and the sector they target.
Kickstarter, for example, focuses on the creative industries, Spacehive on anything happening in the public space and Fundageek purely on academic research projects. Some are very specific such as Cancer UK's MyProjects platform for cancer research, whereas others are general like Indiegogo which funds anything from comic books to funerals. Most do reward crowdfunding but others offer equity like Crowdcube and lending like FundingCircle.
Another important difference is the commission they take from your raise. This usually varies between 3 - 7 per cent. Most platforms tend to operate an all-or-nothing model where you only get funded if you reach your target while others adopt a keep-what-you-raise approach.
Before you launch your campaign, think carefully about which platform will be best suited for what you are trying to achieve, and will help you best reach the investors for this.
Nesta is backing a number of UK based crowdfunding platforms through the Cabinet office Innovation in Giving Fund: buzzbnk which specialises in social venturing, Solar Schools which helps schools fundraise for renewables, and Peoplefundit which supports a range of projects and start-up ideas including creative projects.