I do feel .io is the best choice at this moment...the reason is, it is short and cool, compare with other :
compare with old fashion: like .com, .net, org things....it is cool and represent the new era, and u can find some cool name and even can hand reg the cool name....but for .com, u can only find expensive old name, while more and more new generation choose .io, it will become a trend, people will feel .io is cooler than old guys....
compare with other cctld, like, .de, .cn, .us, it is not like a country-code, it is a global domain, .io is .io, it is not a country code even it actually refer to india ocean, but most people don't look in this way...most people look it as a cool domain..just that
compare with other new top domian, like, .xyz, .blog, .tech, .moda, .cloud, .club, .whatever it is much short and cool....
in a short, I feel .io have its beauty from both techinical and art perspective.....it will become more and more pupular for new generation/startup....but, given it is rep cool, then, it means you should not reg them at a old fasion, like websitebuilder.com may be a good name, but websitebuilder.io may not, similar, afomalindustryname.com is good, but aformalindustryname.io may not good.....so, it will not like .com, it will keep small volume, and rep some thing small, new, unique and cool.....just feel in this way, u know what need to reg and what .io have value and end-user...btw, my own opinion, if its .com version already be very succuss, u may want avoid....there is no too much room for you develop and cool site to compete with that one......
rush to write, may be too may gram/spell mistake, hope still readable.