I agree that, although the two series are very similar, they also feel very different. I enjoyed the Belgariad immensely when I first read it in middle school, and it got me hooked on the fantasy genre, an interest I have kept for more than a decade, but the Elenium, while quite similar, is in my opinion, a better series. In a lot of ways, you could call it a "gritty reboot" of the Belgariad. There is more violence, and the characters are more unphased towards said violence. The characters also aren't quite is overpowered, although still definitely more powerful than the average person. Plus, the series has interesting political machinations with the church leadership and such.
Now that I've typed that out, I have a strong urge to dig out The Diamond Throne tonight.