Personally, I use Sylo, mainly because I like the blue (rather than IP Board's white) and because the comic names on the homepage and chapters on comic pages are more concentrated (no spacing between items) meaning a tighter look.
On the other hand, IP Board is attractive to me because it seems to get more updates and "possibly" functionality. I'm not sure whether the IP Board theme is the "default" theme and if Sylo will adopt all features IP Board will get. I believe so, because Sylo is just a theme.
Edit: the theme option is located at the bottom of the page called "Change Theme". It is on the same line as "Terms of Service" and "Privacy".
Edited by penguin71, 25 March 2012 - 05:04 AM.