Ok, here's my take as a Canadian trying to pickup American stations and Canadian ones as well (who just spent the better part of last night up on the frigging ladder in -20C weather trying to get his damn preamp going)...
Bowtie is the way to go. Channel Master 4221 for suburban/urban areas and 4228 if you're out farther. The latter is more directional and doesn't pickup the side lobes as well. I'm 35Km from downtown toronto (20 miles or so), and much farther from buffalo and rochester NY. With a 4221 I can aim just west of Buffalo and pickup nbc/abc/cbs in full HD glory. My side lobes pickup downtown toronto and rochester.
The poster who pointed out a silver sensor... no good for anyone outside say 15 miles or so. I got one as a freebie when I picked up my samsung hd converter (I only have an hd ready crt projection tv)... he gets... nothing on his brand new 6th generation atsc chipset tv. Well, not nothing, but very little. He gets some of the toronto stations and can barely pull in NBC from buffalo. I ended up gifting him my old 4221 clone for the superbowl, and now he gets most of the stations I get, but is still missing out on some toronto stations.
So, I can say from experience, that the bowtie is the way to go. Which one depends on how far you're trying to "reach" out into the ether.
I can pull in Fox, CBC and CTV with a frigging paper clip attached to my antenna port. The rest, need a better antenna and sometimes even a preamp like in my case. I even tried building a gray-hoverman, and while it was OK, it was far too rickety to put outside. I tried those RCA loop/rabbit ear antennas amped and not... no good whatsoever unless you live right near the transmitter.
Up here we don't need to worry about VHF HI, so the bowtie works fine. But those old huge antennas still work... as long as they are rated for UHF and not VHF (or also VHF if you need VHF HI).
A yagi is great, but is far too directional for most applications... even on a rotor... most of the new boxes and tv's need to be rescanned every time you move it... annoying and takes 2 minutes or so. Good luck using that as a selling feature ;)
My other neighbour has one of those big antennas on a rotor, and his reception is piss poor and it's rated for UHF. The problem is... UHF goes less distance, but is better at getting around objects blocking your path. In his case, we;ve upgraded all the cabling, but it's proably his 4th gen converter box... the newer 5th and 6th gen chipsets have much better mutipath interference rejection which is essential for uhf, and can also work with weaker signals.
Long story short - people WILL need new antennas depending on where they live, and yes, going up a pole requires some scary freezing cold cojones in the winter. I've been doing it for the past few days tweaking my setup and let me tell you... it's not fun. As much as I am not affected by the american switch (aside from reception hopefully getting better once the analog stuff stops interfering - I hope) - this switch will let those in colder climates hopefully NOT have to get up on the roof in this weather.
And, I don't have cable nor satellite. Been free of those expenses for a year or so now.