If you care about socializing, Reboot is probably your best option. This is a picture of the channel populations well outside of 2x (there was not 2x a few hours before this time and there was not 2x a few hours after this time), but this is the most populated I can remember Reboot being. Lots of this is from new/returning players who are here for the V patch, but I really doubt it'll stay this populated.

If you care about making progress in game as a casual player, I think regular servers would be a better option. You need to work for gains in Reboot, but in regular servers you can pay for your gains and save yourself quite a lot of time.

You can be a casual with very little knowledge about the game in regular servers and still be incredibly successful if you put enough money into it (dear regular server people, people don't get upset at what i'm saying here. i'm not saying that regular server takes less knowledge. i know the situation is the opposite: regular server people need to know about a lot more things than reboot people do.). Take this person with amazing gear, for example. He was apparently #1 overall dojo for some time, but has really poor overall game knowledge. This is pretty clearly evidenced by his bossing mechanics and potential choices.