I'd go with the RX200, I mean $160 vs $50+batteries. If price isn't an issue the Volcano Lavabox (which I assume is what you're talking about) looks sweet as far as size, the RX200 is much heftier. But both of them should be more than capable of hitting that 200w limit and unless the Lavabox has some firmware that lets you exceed that, which it should be capable of assuming the specs are correct ( 9v 50 amp, so 450w limit), I'd save the money and just go with the RX200. Then there's also battery life to be concerned about, both will have great life, but even though you can get replacement batteries for the Lavabox, if you went on a weekend getaway how hard is it to replace the battery if you're away from a charger? I know I recently went on one and brought a couple sets of batteries and I was glad I could just pop in different batteries rather than finding an outlet.
Anyways that's my thought on that, save yourself some money if you're just looking at performance, though the Lavabox does look pretty nice.