The arc seemed to have a solid body but shoddy lens cap. My first one was broken there, and my second just didnt seem to be that well made either. It had a nice weight to it, but I just wasn't impressed with the ruggedness.
The jet was more plasticy, but it was a hard plastic, and the bulb end of the unit felt better constructed. I also preferred the beam pattern. Overall it just feels like a better product, to me at least. Customer support from jet was also better from my experience. You may want to compare them side by side. A couple days ago universalcycles had them $325 ish.