Which is better to edit: TIFF or RAW in Lightroom?

I'm new to photography and was recently got a copy of Lightroom to do some photo editing.
Which is better to edit in Lightroom, 16bitTIFF or RAW. I use a Nikon D5100 and need to convert the RAW (NEF) files to TIFF in ViewNX2 to have TIFF files. My goal is retaining highest image quality
Serious answers appreciated. Thanks

Added (1). Lightroom version is 3.6

Added (2). I can edit RAW files but was wondering which is better

So you can't do your editing on the RAW file in Lightroom? That is the purpose of RAW. You edit the RAW file, then save it as a 16bit Tif, (which is certainly of MUCH higher lossless quality compared to Jpeg). You can do further edits in the future of the Tif file if needed in Lightroom without it being destructive editing like you have with Jpeg. But by the same token, if you save your RAW files, you can always go back and have them as your base file to edit rather than the Tifs.

I'm not trying to evade your question, I'm just not understanding why you have to convert your RAW file to Tif in one program and then edit it in LIghtroom. Is is because Lightroom does not support your camera? Can you not download the latest RAW drivers for your version of Lightroom that include your camera? If not, you may find it best to buy the latest version of Lightroom rather than trying to go about this like you are.

steve

ADD: One is not really "better" than the other, they are just different. Here is one way to look at it that might help. RAW is often called a "digital negative", though I don't particularly like that term, but for the sake of discussion, it fits here well. There's just really no need in doing your editing on a Tif file when you can do all the same things with the RAW. Even when you save as a Tif, you still do not have near the ability to adjust things such as white balance or exposure like you do with the RAW file. Now there are some more indepth forms of editing that you can't do with the RAW file, and for that you would certainly want a 16 bit Tif instead of a Jpeg.