You best choice based on your post would be two standard antennas, both aimed halfway between the transmitter towers you want to receive, one pointed halfway between the towers for the US and the other half way for the Canadian stations connected through an A/B switch. The drawback of an omnidirectional antenna is usually its low gain but if those stations are within the omni range and are spread apart on the horizon, an omni directional antenna is a great choice. For my location I've had excellent result with the model found at
www.omnitenna.com