A cone-type will give you more power... as long as it's not heat-soaked... when it's heat soaked, it's not far off from stock... you need to invest in a heat-shield or box to protect it in traffic if you don't want performance to degrade, but it's not really harmful, and you can leave it as is.

A drop-in type will give you less power, but will maintain the stock cold-air tubing, which is better in traffic. It'll also retain your car's stock water-fording abilities. Good if you've got a high air-intake (at hood level), bad if you've got a low one (headlight or bumper level).