(I did take a look at the website and I'm wondering about your personal experience -- what makes a difference in daily use?)
If you do a lot of remapping with multiple layouts or macros the new one is a must. If the occasional modifier's getting stuck really bothers you, or you are a heavy user of the f keys and can't remap for whatever reason you will benefit from the advantage 2.
If, on the other hand, you only do a small amount of remapping and have already mapped away f-keys that are used a lot AND the modifier freezing is not a big deal for you it might not be worth it to upgrade to the new model until your current one bites the dust. If you are looking at getting an Advantage for the first time I would buy this one instead of the previous model.