Are these two cameras really as equivalent as the price suggests?
The Canon EOS Rebel T6 1300D has a smaller sensor (18 mega-pixels) than the Nikon D3300 (24 mega-pixels).
That is not the whole story. The Canon is a newer camera design with newer hardware. Canon designed it specifically for the entry level dSLR photographer. The Nikon D3300 is a three year old design and while still valuable (I use one) it does not have all of the newest features.
Its like trying to compare this year's Honda Accord with a four year old Jeep Compass because the dealer wants the same for both cars.
With DSLRs you are buying into a system You are comparing one element of each of the systems, however when adding lenses/flashes etc into the mix the result could be closer/swing the other way.
A reason someone could choose the on paper inferior camera is that they have friends/family with Canon gear that they would be able to share.