In considering adding a DLSR to my kit, I narrowed down to the two budget leaders in the sub $1000 range, the Nikon D5100 and the Canon T3i. I briefly had the Sony A55 in consideration, but I just feel it falls short in too many areas. I thought the Canon was a slam dunk in every area, but it seems the Nikon does pull ahead in several key points. A much brighter viewfinder, faster focusing, are among some of the most significant Nikon strengths. Seems the D5100 also wins in terms of battery performance by around %50.
Unfortunately, these strengths are almost entirely in the still image department. Canon takes the lead in the video. Nikon saw no need to offer manual control over exposure. Audio control lacks over the Canon as well. Coarse audio control, and metering is left wanting.
A strange wrinkle on the side of the Canon comes from a third party developer. It’s actually a firmware “hack” that adds quite a few features to not only the T3i, but several other cameras. Originally aimed at the 5D MKII, Magic Lantern was developed to overcome some rather surprising shortcomings in the early 5D II cameras. Much to my amazement, the first edition of this camera had no manual control of exposure in “movie” mode. The ML folks not only overcame this, but added many other features. Canon did finally add manual exposure control to the 5DII in a later firmware update.
The benefits of Magic Lantern are pretty extensive, and affect not only the “movie” mode, but add features to the still shooting experience, like HDR and an intervalometer for time lapse shooting. I have installed and have used Magic Lantern myself, and was very impressed. I would however caution all but the most experienced users before marching ahead. Firmware modifications can be risky, and may put your warranty at risk. For more information, visit the Magic Lantern Wiki.
Numerous features and television programs have been captured with the 5D Mk II. As far as I know (please feel free to correct me) it’s still the cheapest full frame video camera by far. For use primarily as a video camera, the Canon T3i is the clear winner. If still images are your main goal, the Nikon edges the Canon out by a bit in that area.