The best smoke is the one that obscures your opponents view, enables you to move as you wish and allow you to see, fills the area quickly, sits in a nice cloud, disperses & clears up, doesn't make a mess or stain, doesn't burn you if you hang onto it, lights first time, is the ideal 'lobbable' shape & size, lands where you intend to throw it, you can happily sit in the middle of it and breathe, works indoor and out, in woods and open fields, does not set fire to dry fields (or even wet fields which can happen) and looks cool.
Simple set of criteria!
Breathing is a key point that can be easily forgotten. Obviously any smoke is not good for you - you should breathe clean air.
I am aware of people having used other smoke devices not intended for paintball, but haven't seen it in a uk game. This is not good, they can be toxic in the short term, leave lasting damage and burn you badly
Indoors smoke should not be used most of the time, in certain circumstances it can be ok, but with close attention to ventilation etc.
Every different colour has its own unique chemical composition (I leave that to the scientists in our sponsors) which means one smoke compared to another may have different properties on duration, thickness,'hanging in the air' etc
The number one factor is always safety & suitability
Only use recreational smoke intended for paintball, airsoft etc