Upside:
1. nice presentation esp. when they bloom
2. convenience of watering and culture
3. take up less space overall
4. cus u just wanna do it and it's nice to get what u want
Downside:
1. they will share disease if it occurs
2. their roots will grow intertwined and could create some difficulty if you wished to separate them down the road
3. larger plants can be difficult to repot
4. if they bloom nice enough that you want to submit for judging, you cannot because it must be ONE plant