best waders??

What is the difference between the simms gortex bootfoot waders and the 
simms g3 guide stockingfoot waders?

Right now I have red ball non breathable bootfoots.  I want to get the 
most comfortable warm waders possible.  What is the reason for the g3's 
not being bootfoots?  I have never worn stockingfoots, what is the 
difference between stockingfoot and bootfoot practically speaking and 
comfortwise? 

What are other waders that are gortex and comparable in quality?