Classic big fish, little pond or small fish big pond scenario.
Might I suggest take into consideration how strong the 1's team will be. Sitting on the bench, playing 5-10 minutes AND losing every week is not good for self esteem.
If they are a strong competitive team and coach is smart, they'll look for opportunities for bench players to play more minutes when they're up 15-20 points. Bench players need a license to make mistakes, that's how they'll learn.
Harder to assess, but look at the team mates too. Playing in VC is awesome, but if team mates make fun of them for sitting on the bench and yell at them if they make a mistake when they are on the court, not a good environment.
Ideally, a lot of development happens at training too.
One final comment, if they do choose to play in the 1's and receive less court time, play domestic and be a top 3 player. I've seen bench kids in VC play domestic with same team mates and they play two games a week and sit on the bench in both, not cool.