My experience as a A3*G and FB Platinum:
- Flying Blue Gold/Platinum is easy to attain and retain as long as you fly business class, don't bother with eco flights. PE is doable. The big advantage here is that XP over 180 or 300 will be transfered to next year(s). Segments are important in Flying Blue and the miles flown to classify the flight as "Medium" to "Long 3".
- A3*G is super easy to retain with economy flights. Not the case with Flying Blue.
- I value A3 miles much more over FB, as award ticket cost in FB miles depend on the ticket price. However, they have their nice promo awards every month with good deals.
- I generally prefer *A lounges over ST lounges, but I assume that's totally route-dependent.
- Star Alliance is bigger than Skyteam, so more "options" for rewards and earning.
- I'm surprised to hear that India is an issue with *A, as they have Air India in their alliance.