Active has a flickering which can disturb some people. With active I get headaches. It depends on your sensitivity.
Also there's a battery in active glasses.
Active glasses are much more expensive. They are often bulkier.
Active glasses are often darker (the lens).
On plasmas which already have a tendency to be darker...active 3d makes things worse by darkening even more.
Passive is like wearing glasses in a movie theater. No battery.
The quality of passive 3d is far superior in my opinion.
I have bought some cheaper $10 glasses as well as some more expensive $70 glasses by Oakley ...they are not dark at all, in fact they are as clear as normal reading glasses.
LG AND SONY AND VIZIO HAVE PASSIVE 3D FOR THE MOST PART.
SAMSUNG, PANASONIC, SHARP HAVE ACTIVE.
There are two types of 3d I want to discuss :
True 3d coming from a 3d blue ray player AND "FAUX" or fake 3d (called 2d to 3d conversion).
All 3d televisions will play 3d blue ray players. The quality of 3d on a 3d BR movie is a REAL 3d effect.
Most 3d tv's also have a feature called 2d to 3d conversion. (simulated 3d, or faux 3d)
What this does it converts normal 2d into a fake 3d.
Vizio does not have this feature. All other Tv's do.
Let me tell you that simulated 3d is amazing. Sony also lets you choose the depth of conversion to suit your taste. Most sony's have LOW MEDIUM AND HIGH.
When i saw this simulated 3d, I no longer want to watch 2d At all !!!!
it just gives the picture more depth...awsome!!
I would urge you to go and see the difference between the Active and the passive 3d...go to any tv store (Hhgregg, BB ..etc)