I have always seen them around the same price ... You may be finding that Canons have more features at times and thus are more expensive. The canon I am looking at is only $500 ... I havent found a nikon that compares
40 gallon - Misc fish
15 gallon - Axolotl
5 gallon - Betta and ADF
20 long - Hatchling turtles and corydoras.
Soon to change I am sure