It really depends on if your using fem or non-fen seeds. If its a height issue 4 plants using lst/sog/scrog would yeild more but if you have lots of horizontal space 1 or 2 plants might be the go. Also if your using hps you can get alot more yeild from fewer plants as the light can penetrate the lower branches much more effectively.

Generally more plants will give you more yeild in a shorter cycle as you wouldnt have to veg nearly as long.

Hope this is of some help