Is the D5100 better for a mostly video, or is the T3i?

Totally right, I checked out both cameras and got a feel for them. I ended up going with the Canon. Im really glad I got a good over-all camera that wont leave me looking for my next upgrade. Thanks for the advice!! And if you want to see what im using it for, check out me and my friend's youtube channel - traitorousdesigns at www.youtube.com

Totally incorrect. Canon does not have AF motor in the camera body; they never did. What both Nikon and Canon have is the AF motor is in the lens, not the body. Older Nikon lenses had no motor in the lens; therefore, they relied on the AF motor in the camera body. Most all newer Nikon lenses have AF-S designation, meaning they have motor in the lens; therefore, does not need AF motor in the body to auto-focus. Another incorrect statement is that Canon auto focuses during video. Wrong, by default Canon T3i disables AF when in video mode; therfore, you HAVE to manually focus if you are moving about as you are taking the video. Nikon D5100 on the other DOES continue to auto focus in video mode, although AF feature is rather slow and clumsy in video mode and its internal mike may pick up AF motor sound during quiet passages.

I really dont know that D5100 has auto focus. I tried to film with it once, but it doesn't auto focus, so I had to press the shutter-release button halfway to focus (My len has no autofocus as well). I don't know if I turn on the auto focus or not, because I cant find that in Menu

If you were using an older Nikon lens, say AF-D or AI-S designation, then it will not auto focus on D5100.

I have checked my len. It is AF-S.

Thanks guys for you input! I ended up buying the Canon T3i. If you want so see what im using it for, heres my friend's and I's youtube channel. traitorousdesigns at www.youtube.com

thats the exact same thing that was happening to me, all you have to do is change the autofocus setting in the camera. Look in the user manual if your not sure what i mean :)