HAve a look at this site and plug in your location:
It should give you a good estimate of the signal strength you get. A roof top antenna will have much more gain than any small indoor unit. If you have room in your attic for a fullsize unit, it might get you where you want to be. That double array in the picture is overkill for the metro area. I recently ordered a Channelmaster CM-2018 to replace a 20 year old Radio Shack antenna. My reason for replacing the antenna is a bit odd as it worked great most of the time. someone in my neighborhood has a really noisy air conditioner that wipes out my reception when the AC is on. Some of the channels have a high enough signal strength to beat out the noise while some are still affected. I'm hoping that a bit more antenna gain might get me over the hump.