I can tell you from personal experience that for right around $1000, you can add a color matched, detachable king tour pack to a Street Glide for enhanced touring capability and an upgrade in passenger comfort. This was worth it for me because I love the clean, no bling, limited chrome looks of a Street Glide and most of my riding is not of the overnight type so the pack will stay off. You can make the tour pack detachable on an ElectraGlide but it will still look a LOT more like an EG with the tour pack gone than a Street Glide.
All depends on the look you're going for and what the main type of riding is that you do.
Just my 2 cents, of course!