Nobody but you can really answer this.
Why do you fancy it?
The biggest difference is really the extra range IMO (if you ignore looks, which may be important to you)
Try riding both new models back to back, that is what I did and if I were to change my 2008 it would be for another (newer) GS, but that is me....
To me the GS feels more chuckable and spritely, not much wrong with the GSA but it felt a little less sporty, on the plus side the GSA felt a shade more plush.
For huge motorway runs and covering massive distances in a day it would be a better bike, but I only do that a couple of times a year so prefer the GS for mucking around locally, and even if I took a GSA all the way to the Alps when I arrived I would miss the sportier feel on the stock bike on the twists and turns.
I also do not commute often which is another area the GSA with its vast tank wins big time.
I also would like the larger luggage, but I understand this could be fitted to my GS if I wanted it that badly, and I would rather do that as a compromise (Stock GS with GSA luggage)
Surprisingly I did not find it much bigger to sit on / manouvre, I was expecting it to feel huge after the GS (It looks a lot bigger) but was surprised to find it feeling almost the same at low speed.
The "feel" can be sorted with a test ride, the practicalities probably come down to your own desires.