Bottom Line: Both the Canon 70D and the Nikon D7100 are excellent and produce really impressive video and stills in low light, and at high ISOs. Focus through the viewfinder is fast on both cameras and it really comes down to the features you are looking for should help you determine which is best for you.

Strengths of the Nikon D7100:

1. Well built with magnesium body, loads of buttons, customization of several buttons and dual card slots. The Canon 70D body is aluminum and polycarbonate. Both are weather sealed. The D7100 offers dedicated bracketing buttons too.
2. Excellent low light high ISO capabilities - I was stunned by the low light performance of the D7100 - high ISO files are clean and the dynamic range is excellent and remains excellent even in lower light. I am listing this as a strength for the Nikon but in most cases the Canon is on par with the quality though when I do see a winner it is the Nikon. If we want to talk about live view focusing in low light the Canon does an excellent job. The Nikon still struggles with this. In viewfinder focusing the two seem equal to me. Nikon does offer the crop mode which fills the frame with focus points, certainly useful for faster action.
3. Images and video are SHARP! Nikon ditched their anti-aliasing filter and the result is sharper video and images AND they still manage to control moire. Even when I try to get moire on the Nikon I can’t - on the Canon I can get it without even trying. It is often avoidable but you are more likely to see it in Canon video.
4. 100% viewfinder- When you look through the viewfinder you get exactly what you see and it is nice and bright. Canon’s at 98% is very slightly dimmer and not exactly what you see - Having that large bright viewfinder is very useful in lower light situations, really helps you see what you are photographing and checking focus.
5. Retouch menu and extra scenes/effects. The D7100 offers a slew of scenes, some of those scene modes that work in video and a robust retouch menu. Now professionals are not likely to be excited by these scenes and the retouch menu but the options are there and they can be fun even if some scene/effects are gimmicky (selective color I am looking at you) - I will also throw in here the dedicated bracketing button that Nikon adds in, nice for serious HDR work.
6. Wireless is a $60 add on and is limited to phone/tablet devices but you can send full resolution files through the air. Canon’s wifi is built in with greater features- including connecting to your computer but you are limited to 1920 x 1080 sized JPEGS that you can send across to your phone or tablet.
7. Uncompressed HDMI Out - this is a professional level feature that allows you to connect an external monitor or HD for recording video straight to a drive.

Strengths of the Canon 70D:

1. The headline feature of the 70D is that lovely live view and video focus - fast, smooth and almost always on target. In the past with a few exceptions live view focusing on DSLRs has been slow, painfully slow and plagued by a hunting for focus, especially in lower light. The updated sensor technology of the 70D fixes these issues. I find myself using live view whenever it is convenient. The 70D locks onto focus smoothly with any lens and gives you have camcorder like focus while still maintaining the beautiful shallow depth of field and low light capabilities that make DSLR video great. Add an STM lens and focus is silent, perfect for the parent who wants excellent video of their child.
2. That live view focus is great and having it on an articulated screen is wonderful.  lift it up, lower it, face it toward you for talking head videos - it just works very well.
3. So i just went on and on about the wonderful live view focusing, couple that with the articulated screen and the fact that the articulated screen is an excellent touchscreen and the 70D is FUN to use - nothing feels like a chore. Touch to focus is useful and if you are doing video work, being able to touch softly to make changes is appreciated and flip the screen around if you are recording yourself for talking head videos like the ones on my Youtube Channel and you can still make changes to settings on the camera - though you cannot start and stop video from the touchscreen.
4. Ergonomics and one handed operation - If you don’t want to use the touchscreen the manual controls on the 70D camera are sweet and with just a finger you push button, rotate a wheel and your settings is changed. Nikon is more two handed in those actions with many buttons left of the screen that needs a push.  Not a big difference and some people  prefer the feel of the Nikon.
5. Burst mode and buffer, the burst mode on this camera at 7fps is serious and the buffer is large enough that you can keep shooting at that high speed long enough to capture your moment. D7100 shoots at 6fps and the buffer fills up in just a second. You can enable crop mode on D7100 which gives you better results but still not great especially if you are using those dual card slots - if faster action is your subject matter the 70D offers the burst mode that you need.
6. Wifi built in with greater options for sharing vs D7100 - Built in Wifi gives you some nifty options for downloading images on the go or direct to your computer(buggy software) or uploading to web services - I am frustrated that you are limited to only transferring 1920 x 1080 sized files and you can't start and stop video.

Longer Bottom Line: Both of these cameras have lots to offer and it really depends on your needs that should determine which is a better camera for you. Parents that want an excellent device to photo and video their children - the 70D really feels like the perfect blend of power and usability, especially paired with the 18-135 STM that will give you silent autofocus. Indie film makers I would think the Nikon with gorgeous low light video and uncompressed HDMI would be what you want. Wedding/event videographers - It can go either way, most professionals I know of and talk to don’t use and are not interested in auto focus during video but I know that there is a group out there very interested in this camera and there are the semi-pros that are interested in easy autofocus while filming and the 70D provides that.  That is just a few use cases. . . Want my opinion on which is best for you?  Leave a comment below and make sure you tell me what you will be photographing or taking video of.  And anything else you think would be helpful for me to know.