Maybe. Neither would work for me though, since I do need a closed headphone with good isolation, and the TH900 isolation is awful according to just about everyone. Other potential upgrades all have issues... T5ps have anemic bass, closed Ultrasone Editions did not impress me at the meet, and Ultrasone DJ Pros/Sigs are impossible to find to demo. And now that I check Tyll's datasheets again, the LCD-XC's isolation is somewhat mediocre, although not enough to be a deal-killer.
I think we're entering a golden age in closed-headphone design, and I'm not the first to note that. Going to be interesting to see what else comes up over the next few years, and maybe one of those will indeed be a no-brainer upgrade.