If you run 600W into the SP210 and then 600W into an OBC210 and run them side by side you'd find that the proper 210 is louder. This is because with the SP210, you don't hear the second speaker as it is behind the first, what it does do though is seriously meaten up the overall sound so that the response you get is nothing like what you'd expect from a 1x10.
I bought this when I was at uni as I needed something small and lightweight that could still be loud enough for proper gigs. And it is, I've used it without any trouble, especially if you're using a head that's 500/600W like an OBT, you'll find yourself having to turn down. Just remember this thing is tiny so you want to be raising it up a little otherwise you'll be playing to your feet.