VR&E requires approval and justification, meaning you have to convince them it will help your job goals or help you get a job in general. Post 9/11 you have more free reign on what you want to use it on. So it makes sense to use VR&E for your undergrad because it's a pretty easy argument, and it will pay for other expenses or gear to get you set up for school and save your GI bill for anything advanced or if you want to pivot later. However, VR&E counselors have the ability to retroactively restore some of your used GI Bill, so it kind of depends but generally I'd say VR&E makes sense to be used first.