quick question for chihuahua owners (long haired)?

how come there is different thicknesses to a long haired chihuahuas coat? like this is a long haired chihuahua yet it has a short long coat if that makes sense:
http://www.pictureperfectchihuahuas.com/Pixie2.jpg

but other long haired chihuahuas have a more thick and fuller coat like this:
http://medix.marshall.edu/~levstein1/blog/Peppy.jpg

is it to do with genetics? grooming? diet? and is i wanted to buy a dog with a shortish long coat like in first picture what do i ask? i have a feeling its to do with the fur being cut and not cut but tell me what you think it is please!

ps. any pics of your long haired chi would be greatly appreciated! (no random ones off google, ive already seen them all!)
oh and thanks steffanie g, i didnt actually realizethat was possible!

I it is all about genetics. Some people breed short haired chihuahuas with the long haired chihuahuas and they get what is considered a half coat. (like the first pic) To get the full long coat like the second pic they must breed 2 long full coats togather. I have a feamale chihuahua she carries the long coat gene and when I breed her with my short coat male we always have 2 1/2 coats and 3-4 short coats. The long haired ones are much more work then the short coats due to the thick hair always needing to be brushed. I have been breeding chihuahuas for the last 6 years and this is what I have found as well as several of my chihuahua breeding mentors.