I've been a long-time fan of both mods (probably about a year and a bit for each? I don't know...). Here's my breakdown.

Both: Excellent improvement over RTW. In fact, it's often hard to say it's the same game when you compare either mod to RTW. Both mods have put in a collossal effort and have achieved great results.

RTR: Fun gameplay, much harder than RTW but still fairly easy to win a campaign. Simple enough to not require much relearning of the engine, and is a "complete" mod. Have lots to look forward to in 7.0, having seen the Dev forum for a while...;) Having said that, the campaign is a bit too easy, DarthFormations needs heavy tweaking to work properly with RTR and some of the factions in the campaign game expand extremely wildly (especially Macedon and Greek Cities - whoever's luckiest tends to end up owning half the world).

EB: Far, far more detailed than RTR, and a much more difficult campaign. For the first time I can think of while playing RTW, I'm actually stuck in a stalemate and am incapable of expanding my empire any further. Eyecandy-wise, EB is better in some respects and worse in others than RTR. Some of the skins are of lesser quality, but the detail gone into the models and animations is astounding. The trait system is more immersive for the game, and the cities are less congested in places. However, it's still a Beta and has lots of things to add and fix. The best thing about EB is, of course, the scripts. From the AI enhancement scripts to the Victory Conditions script, it's all awesome.

Conclusion: They're both awesome mods. EB's sheer detail is both a blessing and a curse; it feels like you're micromanaging too much and need to concentrate more on the traits your generals get, as many are received without you knowing it (such as "Forced March" and "Confident/Unconfident Troops"), but on the other hand it helps make you feel like you're actually running an empire. RTR seems more geared towards conquering, while EB seems more of an empire management game. Both are good in different ways, depending on my mood. As for units, in general I prefer RTR skins but love some of the new anims for EB (especially the two-handed Sarissa anim, despite the bugs). So, while I'd say EB has the most potential, it still feels incredibly incomplete, as one would expect in a Beta. For completeness, RTR is the way to go.