Part of the reason there is more info about Lightroom out there is that it is available for both Windows and Mac. By itself, that virtually assures there will be many more LR users, therefore much more information being presented.
It is also true that LR4 has added some capabilities that would seem to offer much more than the current verson of Aperture, especially regarding RAW image processing. But these features come at a price...and that is performance. There are many LR users with serious performance issues using LR4...take a look at the LR forums if you haven't already done that. And be sure to take advantage of LR's 30-day free trial before you purchase to be sure your hardware is up to LR4's requirements.
I have heard good things about the Nik HDR plug-in.
Here are. This is one of the areas in which Lightroom far exceeds what is available for Aperture, for the reasons phosgraphis mentions in .