The infocards are generally pretty informative. When you have a planet bonus, below the name of it will be its effect, in this case it would read something like Gravity Well 33% (in red) meaning decreased (green means increased).
Also all the planet types and "special" celestial bodies (magnetic clouds, storms, suns, gas giants, etc) can be selected and they have a passive ability button that shows what they do.
For your question, different sun types don't do anything different from each other other than look pretty. But all of them increase antimatter recharge rates in their grav wells.
