Space habitats are a better choice.
There are numerous reasons for that.
- flexibility in desired results
- speed of achieving the desired results
- material efficiency
- very high theoretical limits for resulting surface area for the approach
- flexibility of clustering those constructions (ability to pack vast amount of people and surface in planet size conglomerate if one would wish so)
- Full control over created environment.
- Effectively no physical borders for the group, preventing their grow/extension as a social group.
Mobility is a good thing as it allows to choose locations(planets), distance to a star, distance to neighbors etc.
Flexibility in results - one can choose gravity, day/night cycles, weather, climate.
Ability to choose/create particular flora and fauna to live in. (Would like to see how it was in dino time to live - resurrect all those animals and well go test/see that)
The result can be achieved pretty fast, in a year or two(in certain cases even faster, in some cases slower 10's of years) instead of a long time for planetary situations even with proper technology it will take a long time to replicate earth like system just because it needs time for the planet to settle down after intervention and all doings.
Material efficiency - the materials which have to be spent on building a space habitat are in the range of 100-1000 tons per human(based on O'Neil project, it might be more or less it depends on the technology and result we would like to have). So a space body like the Moon would be enough for about 6-7 orders of magnitude more people than there are currently living on the planet.
If one would like or if it would be needed with proper technology all those space habitats(made from the Moon with 1016 humans) could be collected in pretty compact configuration, they can be placed in a sphere of a few thousand km in diameter, allowing them fast information and matter exchange.
Space habitats offer more flexibility and freedom of choice, where using of planets needs definitely not fewer efforts as it goes for technology and environment. A planet might demand some compromises, just because not all of its aspect might be accessible/controllable even with pretty advanced technologies - insides of a planet as an example, which affect different aspects of its behavior on the surface and it takes a long time to change things and for them to settle. Because of the pressure, certain parts of it might be not accessible at a required level of influence, when those processes could be manipulated/supported in the way they should be.
Everything has its price and a planet a pile of materials pretty much maintains itself for a long time, where a Space Habitat should be probably maintained regularly and constantly be monitored. However, maintenance task might be not that hard as it looks now it has to be, and it can be done with realistic(my opinion) means of ... hm it seems I can't avoid the word ... smart matter. I assume the option as realistic because I keep in mind particular implementation of such technology which is not that much sophisticated, definitely not a clarke-tech, and pretty much fits in +200 years theme and for it, maintenance would be not a problem.
But even without smart matter maintenance is pretty manageable subject, with a variety of different approaches(those I also keep in mind at least 2-3 of them).
I'm all for the Space habitats, they offer too much for too little, and planets are just a source matter for them.
Most importantly they offer flexible borders(because of there none of them), and freedom to devide the group which can be done easily and fast(opposite is true too). Those things they are important, and they can't be realized on a planet (or it will be not a planet in the sense we usually assume).