All things being equal, the planet that got 40 production likely has a moon. That'll give an additional production bonus. Planets with rings give extra research.   

...ethical choice when colonizing as well may have a factor.

If you zoom in to the planet you can see if there are rings or moons.

Asteroids can be made in TA by blowing up a system with a Terror Star. Each planet becomes an asteroid.

Unless they've finally fixed it in TA, for a long time, rings made no difference to research bonuses.

You could have picked an ethical event choice screen that would increase that planet's production level.

Other things to know about Planet Quality

Lower class worlds have a growth limit that they will not grow beyond. For example, a Class 3 world has a limit of 1.32Billion

Everything Class 11 and higher receives a Morale Bonus for being a high quality planet. This is a flat bonus making it very powerful.

Only worlds higher than I believe Class 6 can have bonus tiles on them. You will not see tiles on worlds lower than that, even if you have the Neutral Alignment/Terraforming Techs that instantly upgrades them.


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As for specialization: Look to whatever bonus tiles may be present and let that serve as a guide to what should be built. A world with a 300% manufacturing tile would be better served by a factory than a lab. Things like that.

Clarification:

Terraforming Tile: The Yellow, Orange, or Red tiles that require a tech to be available to you

Bonus Tile: A tile that has an icon on it such as the 100% Manufacturing Bonus

Under the Neutral Alignment, once Xeno Ethics has been researched, all existing terraforming tiles are automatically upgraded provided you have the requisite technology (ie all Yellow Soil Enhancement tiles would be upgraded once you research Soil Enhancement)


Any low-PQ world you colonize will not have any bonus tiles on it. That is, if you colonize a Class 2 world, it will most definitely not have a bonus tile. I believe once its starting PQ reaches 6 (though it could possibly be 5) that there is a chance it will have bonus tiles.

Now later in the game, assuming you went Neutral or have built the Orbital Transformer Wonder, and you colonized a Class 1 world, all its terraforming tiles would instantly be upgraded, making it a possible Class 10-20. But its BASE PQ is still "1" and so it will still not have any bonus tiles.