I'v got me a Sartek 10w adjustable with the LiOH battery. Wow, talk about a small battery case. It fits in my hand. Half the size of a NiMH case for four hours burn. The only downside to the Sartek I have seen is the switch on the battery (although I'll be wearing mine on my waist, so no big deal - not so fun for backplate mounted bigger batt packs) and the light head allows light back through the lens cover (you can see a corona effect if you look at the head from the back) Not a big deal, but it could cause night vision issues with the brightness of it. Other than that, it's rugged (I watched Carl from Sartek jump on a demo a few times. Still worked.) and it's weight and size are nice. Now all I have to do is get a handle for it (no goodman included, just a gear clip).
My buddy dives the OMS (new style) and just bought a Sartek himself to compare. He says he'll probably stick with the OMS, due to the switch on the light head and the overall construction. He says he likes the fact the battery cord runs through an effective LP hose. This removes those pesky exposed bulkhead penetrations on the head and battery.
Of course, he's also thinking of trading in his Sartek NiMH for a LiOH battery pack. So, all in all it probably comes down to a 10W is pretty much a 10W, and so forth. The car charger for the Sartek LiOH is nice, though.
Edit: One thing I forgot to mention....the biggest downside to the OMS light I've seen....is that I haven't seen an OMS light in quite a while. Seems the things are on permanent backorder.