IGPX: Immortal Grand Prix

Most of the similarities lie in the mecha designs and style than anything else, but if you're into the genre, this is probably one of the reasons you watch a series. I wish that IGPX went with the pilot, but I was still satisfied with the end product. Anyway, a mecha battling arena plays a big part in the earlier portions of Votom's story, and acts a teaser to draw you deeper into the universe. 

Both have high amounts of action with mechs. Even though IGPX is a very short arena battle type series the mechs seem quite similar..