Which Tv Antenna is best with obstacles and multipath for DTV?

Hello, I live about a 3 minute walk from a tall hospital and smoke stack. I'm having problems with digital and og TV reception. My current setup has an unamplified VHF/UHF antenna strapped to the chimney. When installed, the installer had to try about 4 different antennas due to the multipath. This setup is now 7 years old. When split more than once, performance really drops. I have stations that I should receive, that I cannot. They are less than 20 miles away. The antenna is too low, I have several houses, trees and telephone/light poles that are taller. So, I'm getting a 40 ft tower, a brand new high powered antenna, rotor and preamp professionally installed. So my question is, which antenna is best for mostly UHF reception when multipath is an issue due to the hospital? I believe one of the digital stations might move to channel 7, but it is only 15 miles away. The new Winegard 7-69 channel antenna? Thank you.