7-9 slot has the better chance of getting a large planet.
i like 10-15 for the deuterium, but theyre usually small. 1-3 are worthless. even if to make solar sats and try to get graviton tech. dont ever colonize there. 4 is good enough and wont be 15 fields big lol.
the solar bonus goes to solar sats only, not your solar power plant. you shouldnt really make more than 25-50 of those b/c the debris is pure crystal and ppl will look for that. theyre also the first thing to die in any battle!
the further from the sun the more deuterium your deuterium mine pumps out - for the same cost/energy consumption. im actually flying to my 4th colony now in the 13 slot. w00t