I've played EB since 0.82 and frankly, it is the more robust total conversion. Played RTR until the wait for 8.0 became overburdening and I got enough of the superstar attitudes some of the mod members had and I haven't been to Total War forums in ages, but I reckon they are still in Platinum edition, right? It's a great mod, but I wouldn't play it without Metropolis and Naval mods("metronaval" affectionally), since Platinum offers only very stock features, nothing you could not find in other mods nowadays. Kind of ironic, since it was RTR which originally introduced those ideas, like the large map, cultures having an effect, area of recrutment and auxiliaries. However, Europa Barbarorum not only reworks the game visually and aurally(like RTR Platinum), but it also adds a host of interesting features to the gameplay. A lot of these personalize the game further, making your leaders more important and prioritizing planned conquest and cultural improvement over blitzing the whole map. Then again, it's a very slow game and that's not everyone's thing.
I'd play both and see which one you prefer. Just remember, a lot of mod devs have a dream of closing the boundaries between TW and Civ games and that's not something that is going to happen with such a hard-coded engine as RTW. It's a military conquest game, the AI just can't take diplomacy or any other option.
Edit: MOLOSSON AGEMA! MARCH! KATAPRAKTOI! CHARGE!