I'm a little confused on the difference. I'd assumed the Supporter Bundle was simply SPG3 and the Supporter pack however the price to purchase the Bundle exceeds the price of purchasing the game and Pack separately.
Support Pack is a DLC which adds the Starpoint Gemini 3 official soundtrack composed by Nikola 'Nikita' Jeremić, digital artbook and four weapons with different 'skins' to your game in the freeroam mode.
Support Bundle is both the game and the Support Pack combined. The price of it should be slightly lower than buying both items separately. I don't know if there's any difference with regional pricing, but for me it shows that the Support Bundle is cheaper than both the game and Support Pack combined.
Regardless if you decide for the regular game or the Support Bundle, if you get either of them by October 5th, you will also receive Starpoint Gemini 2 completely free.