To start, here are the technical specifications for the Canon & the Nikon.
The differences are a bit staggering. You said you used to shoot video, but now want to focus on photography.
The Canon has a significant advantage over the Nikon, by having more than double the megapixels, 18.0 vs. Nikon’s 6.1
The Canon offers a much faster shutter speed & an ISO range of 100–6400, which is excellent for low-hi levels of light. Nikon’s much smaller range is 200–1600.
A quick price comparison on Amazon has the Canon (body only) being about three hundred dollars more than the Nikon (body only). While a few hundred bucks is great for someone wanting to get some quick spare changeā¦ the savings is just not worth the decrease in quality of product if your purpose is to focus on photography. And if you decided to shoot video again, you wouldn’t be able to with the Nikon.
The only reason to downgrade would be the need for instant cash in the pocket. While the Nikon is a great camera in its own right, if you downgraded now, it will cost you a lot more in the future to upgrade. Re-selling the D40 wont get you as much cash as a 60D.