If possible, give him the opportunity to read through the book so he can see how the game has changed. A lot of the changes sound drastic and jarring if you're just hearing about it second hand (like fewer "core" classes) but once you've read through things to understand how the game was restructured, it starts to become clear exactly what the game is trying to do. I'm assuming that none of you have actually played a game using Saga Edition, so get the group together and let the GM know that all of you are willing to work together to learn the ins and outs of the new system.
If you're looking for specific selling points on Saga, that is tough because there is so much that makes Saga a good game. For the most part, its strength comes from the fact that a lot of rules systems that were needlessly complicated or given their own obscure rulings were streamlined and made quicker and easier to remember and reference during the game. The core classes were trimmed down but at the same time, they were made more flexible through the ability to select from the various talent trees. Even two characters taking the same class can have entirely different play styles based on the types of talents they choose.
Combat rules are quicker, easier and more intuitive, the new Force Power design is a lot of fun but still fairly balanced against the other classes.
Talents are one of the coolest new elements of the game.
Also, character creation is considerably quicker in Saga. Even creating high-level NPCs can be done in 30 minutes, so it makes it easier for the GM to put things together.
The ship combat system has more options than the previous version, in my opinion, yet is still simple enough not to bog down the game.
There's a lot that makes Saga good, but I think the best path is to sit down with the GM and look over the game together. Point out the cool stuff and share the enthusiasm. Hope that works for you.
HARRY DRESDEN — WIZARD
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