This should open up a big can of worms... as every one has their own opinions and preferences.
I went with an edge evolution cs for 2 reasons, the price was great ( got it second hand), but most important to me was the custom dash pod to mount it to the dash.
I originally used it in economy mode and noticed firmer shifts and maybe a slight increase in mileage.
When I put it to performance mode I wasn't sure if I could feel any huge difference until I turned it back to stock mode (for a dealership visit)
On my way home from the dealer I tried to pass a transport on the highway and then realized how much of a difference it really does make! Needless to say I immediately switched it back!!!!
Below is a picture of the dash pod with the programmer installed.
(I have since removed the programmer and placed my GPS in that location... I really miss all the info provided by the programmer, but it was too bright at night on country roads)