I do believe that the answer to this question depends on your needs and priorities.<p>For instance, you could be asking "which country will charge me the least tax?" Look for a tax haven, like some of the Caribbean islands.<p>But you could equally be asking "which country will provide the fastest internet speeds?", in which case it's South Korea.<p>The list of considerations you might be using to filter your decision also includes paperwork (at start-up and ongoing), access to mentors, fastest access to the largest number of users, or even language and lifestyle (if you wanted to live or spend time in the country). Some of these will differ again depending on whether your online software will be B2C, B2B, or Enterprise focused.<p>Are any of those factors for you? Are there others?
It's undoubtly the country where you love to live. Since tax and other technicalities are irrelevant compared to YOU feeling good and not not having to worry about nothing else but software.<p>EDIT: Removed some useless stuff.
Wherever you live. If your country of residence is highly bureaucratic or corrupt, you may wish to incorporate as a Delaware C-Corp or a British Limited Company.