Here are a couple key differences:
Xenarcs can accept unregulated 12v straight from the vehicle electric system.
Lilliputs require regulated 12v power (despite the fact that many users run their Lilliput off of unregulated 12v power with no apparent issues.)
Xenarcs will auto turn-on when they receive a signal.
Lilliput monitors don't.
Some time ago, Lilliputs suffered from quality issues. I don't think that those are applicable any longer. Although, I must say that I see more users having problems with Lilliput brand screens than Xenarc brand screens.
Take that information any way you choose.