The older I get the more that the artistic side of my brain is taking over from the engineering side.

The best bike will always be the one that brings you the most joy when you use it. Certainly, if it's seriously unsuited for your route to work, or if it breaks down all the time, that's not going to be good. Within those parameters, however, which bike sings to you when you look at it? Whether it's due to the color or graphics or just the stance or whatever other reason, the bike that makes you feel good when you ride it will always be the best one.