(...a lot of really good thoughts about JOATs and luck...)

• The non-JOAT has to build a few more colonizers and freighters, since he has to take over a few more planets than the JOAT does. But that's a pretty small cost in the overall picture.
  
• The non-JOAT has to spend a few more years bombing out abandoned planets. Okay, yes, that's a pretty good point. Moving the bombing fleet around takes the non-JOAT a few more years, so the JOAT benefits from his gains more quickly than the non-JOAT.
  

• I agree, but I don't think this advantage is restricted to border planets. If we accept premise #1, that the JOAT has tighter habs, then finding a good breeder is already more beneficial than for the non-JOAT, even though it is just as likely to occur.
• If the JOAT is 45 wide in all 3 habs, and the non-JOAT is 50 wide in all 3 habs, and both are centered the same, a great planet (+-5 clicks from center in all 3 habs) for one race is also a great planet for the other.
  

• 1 in 93 planets will be habitable according to the RW.
  
• If you find a great planet (+-5 clicks from center) close to your HW, you have exceeded your average expectation by an enormous amount. You weren't even expecting to find one habitable planet within 3 hops, and here you have a great one. Extraordinary luck!
  
• Now you can export pop when you hit 25% on your HW, and pretty soon you'll have twice the pop growth and twice the resources and minerals than you were expecting to have with average luck.