Compare the price between 4x HD and Nexus 4. If Nexus 4 doesn't cost more than 20% than 4x HD. I prefer to have Nexus 4 instead.
I am owning 4X HD and my sister has Nexus 4.
Nexus 4 has a better build on everything. It has much better hand feeling, better CPU, it has 2G of RAM, less heat, seems better battery life + you will always get the latest Android version from google. The only thing I don't like is it's onscreen button that actually make your viewable screen size smaller on most of the apps.
To be honest, 4x HD is not outdated yet, but 2G of RAM + Snapdragon s4 CPU really beats 4x HD up a lot. If it is possible, try it with your own hand, open up some web pages with chrome, you will know the differences.
Please dun get it wrong. I still love my 4x HD, it is still the best price/performance phone now. Just if your money is not that tight get a Nexus 4 will be better.