Frankly, I overall like Eureka more, but I adore the fact that you can't rank down in Bozja, a big gripe I have with Eureka is that I can level down if I am not careful, which is just an uncomfortable thing that prevents me from getting experimental, it's not hard to get that level back up, sure, but it is annoying, and I get it's because it's that way in FFXI, but that's a system that I frankly think sucks and MMOs have largely moved away from.
Not just that but it is something *completely* unnecessary, you can clear everything Bozja related without it, with much less in fact, it's just there so you can feel good for yourself and be proud of something, which is what a good grind should be about.