Building a 2M 70cm antenna for fixed QTH. I assume that vertical polarization is more common as anyone using a mobile rig is probably using a vertical whip.
I am in MD near Washington DC. Would you go vertical or horizontal?
What's your operating goals? Talking via repeaters to the mobilers or vhf/uhf DX'ing?
If it is the former using FM, then KB4QAA is correct.
If it is the later, then Horizontal is the way to go, but includes CW also (the real VHF DX'ing).
Are you planning to interlace the elements?
You could also construct a swivel mounting where one could switch between vertical and horizontal polarization for the best of both worlds.
GL, 73, Rich, K3VAT