Writing, Campaigns, and a General Roleplaying System

All righty. I have been considering my setting, and expanding it to a depth that would involve, essentially, me writing a good amount of the campaign from the ground up. As a result, I have decided to look in to buying a General Roleplaying System, where the rules are comprehensive enough for me to write my setting and world as I please, but without an established setting to limit either rules availability or my own creativity. Don't get me wrong, I still plan to buy v.3 when it comes out, but I'm kind of curious to see what sort of setting is there, and how well it works. Also, the two general systems can work well for all sorts of settings. The ones I'm thinking about are GURPS and Hero v.5. I've played a game based on Hero, Champions, and thought that the mechanics, though a bit complex, worked very well, and allowed for a great amount of flexibility in writing and running games. I have not played with GURPS before, but I have heard many good things, and it seems to be just what I want. I have not decided yet which to consider investing in, but as both seem to be good systems, outside input would help. As of yet, I have not met someone who has actually played both, but hopefully I will get some idea which works better for my purposes.