Other than the fact that they are both single AA cell LED lights, they have pretty much nothing in common. The L1P is probably 3 to 4 times brighter and really needs either an NiMH cell or a primarly Lithium cell to do it's thing best while the X1 can be run absolutely just fine on an alkaline cell. Runtime of the L1P on an alkaline is going to be about an hour while the X1 will run for probably 4 or 5 hours to 50% brightness and will put out enough light to read by for close to a day.
For general quality, they are both great, but I'd lean towards the Inova. It's been long my favorite 'feeling' pocket sized light. The glass lens is nice, the tailcap has been VERY reliable for me though not everyone shares my experience and some hate the twist on tactical type action. The Fenix is close, and I'd be hard pressed to actually complain about it, but I still prefer how the Inova feels.
For beam... the new X1s wil have a bluish center and a greenish-white spillbeam while the Fenix is at the mercy of the Luxeon lottery. I've had good luck with the Fenix lights I've had. While they have different tints, unless compared to seomthing else, I've been happy with all three of my L1Ps, my one L0P, my one L2P and my two L1 non-premiums.
Overall, for me, it comes down to brightness and runtime. If you want something that is usably bright and will run for 5+ hours at good relative brightness, go for the Inova. If you want something 3 times as bright that runs for 1/4 as long, get the Fenix.
Or be a
real CPFer and get both.