HIDs will install just fine in the headlight housings. I havent done it myself yet (although plan to), but very little modification is usually needed to adapt in a HID. I know on my 2010 Ram, it was all plug and play pretty simple. On the reasoning of illegal, like stated above, installing LED bulbs are illegal as well as far as I know. Also, HID output is far greater than LED at this time. From my research, LED kits are around 40-50% less lumens than HID.
Regardless, if you want more light output you should goto HID. If you are looking for a little better spectrum and color change, just get some Silverstars. I see no reason to use LED lighting at this time considering a high quality custom job will run you a buttload and a cheap kit is about the same as a high quality HID kit.