jquery is used by the ruby crowd,
while generally speaking dojo is used by the python crowd.
Ok changing now, but that is the way it used to be

I looked at it ages ago.
As a result dojo is heavily influenced by python, if i remember correctly is was developed by python coders.
For dojo, you have to use their method of declaring classes. It attempts to make thier classes "python like".
It is almost a full fledged framework. It intrudes heavily into the JS.
If it was a huge project, it might be a good idea, but for most things it is just overkill.
In comparison jquery is basically a "cross platform library". It is a very thin library.
Also jquery can be run in its own namespace so it plays nice with other libraries.
IMHO you are better off to use jquery and js prototype method of "classes".
As me and perks discussed, there are numerous ways of implementing a class system.
Unfortunately people only know the "C++" method of classes, and think it is the correct way.
Get perks to explain how prototype "classes" work

(i put "classes" in "" because prototype system does not really have classes, you basically just have objects and are "cloning" them).
From a speed perspective a prototype object system is much faster, simpler to implement, and more flexable.
That is why JS used a prototype system.
Under the hood, the "window class" does not exist. There is a "master window object", when the browser creates a new window.
It will clone (copy) that master window object. Then at runtime it adds the extra methods for the cloned window.
This is much quicker. And more flexible.
Anyway my 2 cents.