In the 65centimeter GMRS band, height means more than anything else for your antenna as long as your coax length is less than 50 ft, then coax quality begins to inch in, but height is still the prime consideration.
If your area isn't generally flat, even a well elevated antenna will not propagate well in the obscured directions; a repeater does not overcome this unless it is located at a centrally located high ground location. The advantage of a repeater is to generally double the range of 2 mobile radios. If the repeater antenna can be located on a tower over 150ft high and the tower itself is on a locally high elevation the range between the repeater and regular stations can be 20 miles under perfect conditions. At 50 ft elevation the range of a repeater is more likely to be less than 10 miles, probably 5, sometimes even less with buildings and trees around.
Good brands of antenna are Diamond, Comet, Browning, Tram, Ed Fong. There are many to choose from among these brands.