head has a longer muzzle and and not quite as large and rounded head so they look alot like a deer's face. A applehead has a larger, very round domed head and the muzzle is much shorter and usually thicker.
Keep in mind with the breeding now days there can be such a variation of the size and shape and it can go from one extreme to the other, you can get a mix between the two where it isnt as easy to really tell what they are closer too
Yours is awfully young to tell right now, Do you have pics of his parents?
My Yoshi is very deer faced and is not cobby at all but at the same time he doesnt have long legs either.
Here is a link to the Chihuahua illustrated standard and this will give you a better idea of what an applehead looks like
There are quite a few pictures and views of the head
If for some reason the above link doesnt work then go here and click on what says the illustrated standard
I am trying to find a good picture of the deer type.