Here is a picture from SignsDirect.com that shows both styles side by side.

The feather flag has a looser motion in the wind.  The bottom corner that is away from the pole is floppy.  That could be considered good or bad depending on who you ask.  The motion in even the lightest breeze can be seen as grabbing attention as people tend to notice motion.  The down side might be that in high wind it flaps hard making it slightly less readable.

The teardrop flag doesn’t have a “floppy corner”. The teardrop flag is stretched tight from the tip of the pole down to the lowest point on the flag.  Therefore, the message is always pretty much stretched tight and wrinkle free.  The down side might be less motion …especially in the lightest of breezes.

Both do a great job of getting noticed as long as you change them up at least once per summer.  People stop looking at them after they’ve already been noticed repeatedly. I’d suggest having a spring feather flag, a summer feather flag and a fall feather flag.  If you want them to be noticed even more, switch between feather flags and teardrop flags with the changing of the seasons.