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In the States UHF stations that used a pylon type of antenna also transmitted with some vertical polarization, while VHFs used almost exclusively super turnstile antennas which were horizontally polarized.
BUT, transmitted polarization is really not important as the wave undergoes all kinds of rotation in the field.
In the early 80's some stations switched to circular polarization (particularly hi-band VHFs). The benefit was that it would get more signal into valleys and had the benefit of ghost cancellation. The circular polarization would reverse phase off the reflected surface and cancel out at the receiver's antenna.
BUT, even more importantly, was the fact that the FCC would allow you to run more power. So, if you were running 100KW horizontally, you could run 100KW vertically also, if the station could afford the added electric bill.
Technically you had 200KW in the air (not counting antenna gain to make ERP).
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