I can only really say from my experiences with both versions of debian, what the perceived differences are.
OABI (Titchy usually) seems to run slower than EABI, in that for instance during installtions I had noticed a pronounced difference in time to do major installs. Download at the same speed, just the configure and setting up stage was slower.
There are more apps for OABI in the repositories, BUT there are a number of them that don't run as expected. Or I had a really bad run of luck with apps I wanted
Sound support (at the time I installed OABI) was abbismally bad. Hardly working at all, now I am not sure this has been fixed yet. In EABI it works nearly as well as in PdaXii13, and slightly better than PdaXrom 198. At the time this was a deal breaker for me with OABI, with Zdevil's help I got sound working on EABI and have been happy since.
EABI does seem to have frequent bouts of this program or that program can't install due to depencency issues. It can be very frustrating, where as OABI seems to have few of these issues. On the good side, if it installs it works as expected.
Other than that I have not seen a large difference.