There is quite a bit of difference between the formats.
The DSLR is great for shooting narrative work where you plan to cut multiple scenes together. It shines if you need to have control over the visual style that is achieved with depth of field & interchangeable lenses. The relative weakness (for some people) is lack of good audio inputs (no XLR), lack of good autofocus, especially for fast moving subjects. DSLRS also have a tendency to create moire and noise due to the size of the CMOS chip and downscaling the resolution. You also have to deal with the "jello" effect on side pans. Shooting on a DSLR is a lot like shooting with regular movie camera - plan to have a focus puller, and limited record time AND limitations on editing codecs. You also can't shoot by hand due to camera shake - you would need an expensive steadi-tracker/shoulder rig or lock the camera on a tripod. If you can live with this, then the DSLR shoots beautiful footage, but only if you know what you are doing.
Video allows for more continuous action and longer record times. You also have excellent autofocus and XLR inputs for capturing great audio to the camera as you record (whereas, the DSLR audio is best captured from a secondary recording device). Video is easier and somewhat faster to work with. It's excellent for documentary, weddings, news, etc... The drawbacks (for some people) is that video looks like video. Unless you buy an expensive ground-glass focusing device, you'll have little control over depth of field. Unless you are willing to spend a lot of money, you also won't have interchangeable lens. The plus side, is that you have better options for zoom and you don't have to buy extra lenses. If you want a "film look" on video, you have to do a few tricks to make it look like film. Some can be done in camera and lighting, and others during the editing process. Oh... and one more thing that is kind of debatable. Video cameras have a tendency to have more noise in low light situations. Of course, that depends on which camera you buy! However, video cameras are easier to light for.
In summary: if you are looking at shooting stuff that gives you the greatest creative control and looks more like it was shot on film - then buy a DSLR and prepare to deal with the short-comings of the format and the relative expense of buying accessories (they are more expensive than video).
If you are looking at shooting documentaries or anything that requires a run-and-gun shooting style... AND you don't mind the look of video, then buy a video camera. The final caveat to that - in my research, I have found that video cameras that compare in visual quality to DSLRs cost 2 to 3 times more than DSLRs. Although, you do get more in return.
By the way... the RED Scarlet is vapor-ware. They have been talking about it a long time now and many people think it's not going to happen. The DSLR market is moving much faster and RED just can't catch up. But if it DID manage to get produced, you would be looking at several thousand bucks just to get a basic setup. If you are willing to wait for RED, then you might as well wait to see what Canon does in the coming year. The RED scarlet would be over-kill for most people.
