first let me say that i like ALL mustangs regardless of year, and yes that includes the mustang ll. i own a 66 coupe and i can tell you that the reaction i get when i drive it is nothing short of amazing. everybody and their relatives, with very few exceptions, loves the car. i personally would love to have a 2005 mustang
as well. i recommend that you try on each car before you buy, and if there are things you hate about the car, dont buy it as you will regret it later if you do. have any used car checked out by a competent mechanic, and one that is not connected to the seller.
some things to consider though about the vintage mustangs;
1: rust. ford didnt do much rustproofing in the early 60's.
2: suspension. vintage suspension systems are not known for their ride qualities, especially in vintage mustangs. also vintage suspensions tend to be worn out on less expensive cars.
3: drivetrains. engines, transmissions, rear ends, etc all tend to be rather worn as well in the less expensive cars.
4: interiors. also worn, and again not as comfortable as the newer cars.
if comfort is important to you, then go with the newer car. if not then the vintage car is the way to go.