All the window variables are as fast as the finance variables. However, even people who use finance variables don't use them, because the most well-known ones (the X- and Y- ones) mess with the graph screen. But wait! There are some window variables that are only used in parametric, polar, or sequence graphing mode. All of the T-, θ-, and n- window variables don't do anything when you are in function graphing mode (normal mode), so they can be used, like finance variables, to increase program speed.
This means we have a ton of fast variables!!!!!
Obviously, we can't use all of the window variables, because some are only for TI-82 "compatibility", and some will update the value of other variables, but there should still be enough that you won't have to use normal variables anymore (except in for loops).
Also, they are faster to access, because you don't have to wait for the apps menu to load!