The Advantage Of....?

I've been getting heavy into Tournaments on multi US sites. Carbon, Bovada, Black Chip etc etc.

I always pre-register for tournaments I would like to join in advance.

I see the same kind of tournament listed in different ways.

Example:
$1,000 GTD... $2 Buy-In (700 players when its all said and done)
$1,000 GTD... $11 Buy-In (100 players when its all said and done)
$1,000 GTD... $66 Buy-IN (40 players when its all said and done)

All 3 are starting roughly at the same time.

Other then the amount of players (less is better). What are the advantages of joining the $66 Buy-In instead of the $2 Buy-In, when the GTD is the same?

That is pretty much the reason. If there are 700 players, you could be playing for 3-4 hours before you even cash and the only time the payout is really worth your time invested is if you final table (even then, sometimes top 4 is all thats really worth it)

The 66 buy in with 40 players your hourly rate becomes higher.