"Can someone please explain the difference in the 700 VS and Sendero? "
Yeah....the Sendero is a "long action" action that will take the magnum cartridges such as the .300, 7Mag and the long cartridges such as the .25-06,.270 and .30-06.
The Varmint Special is a "short" cartridge rifle that takes .223, .22-50 or .308.
Thats pretty much it.
I have a .308 VS and a Sendaro in .300. They look identical other than the lenth of the action. Both are absolute tack drivers.