For web surfing and office documents, the higher res display on the 15" is probably unnecessary if you're strictly budgeted. Some of the people to whom it's most important are people who use 1. multiple programs at once that show live data that you want to watch and 2. art production apps, like CS and Final Cut.
HOWEVER - the higher resolution display WILL make a difference. It will definitely improve your workflow simply because you can fit more on the screen, and it will make reading and writing smaller text and watching high res videos much easier. It's certainly optional for you, but I'd still consider it if you have the budget because it will definitely improve your overall experience tremendously.