One way you could figure out what you want to do is to recap what you each did first and then figure out if there were any gaps in the offerings. So, "I was a developer, but my clients always wanted X." or "I was a designer, but I wish I had X." What tools did you each lack? What did clients want in addition to the service provided? If you find a common ground here then you're creating a business that is really needed in the market instead of replicating what's out there already.