Caveat: It has been nearly 20 years since I was in that business.
Rainbird, Hunter and Toro are all fine equipment. You should be fine with any of them. When I was bidding jobs, we used a 1/3 parts, 1/3 overhead and 1/3 profit breakdown. The price difference for you might be based on how much overhead and profit they are figuring. The equipment costs should be similar, regardless of brand.
The number of zones is based on how many g.p.m. are needed and the size of the pipe used. In OK, most res. systems use a 1" main (your meter is usually 3/4 to 1"), with 3/4 and 1/2" pipe feeding the heads. Spray heads are a good idea for any area less than 20' wide. Make sure the design calls for head to head coverage, i.e. each head sprays all the way to the next head.
Some runoff is to be expected, especially if wind is an issue. In OK, it is usually windy, and so impossible to avoid spraying the street, etc. The use of impact (rainbird type) or stream spray heads nearest the pond should help minimize this.
Another consideration is where the valves are located and the type of backflow prevention used (usually set by code). If your valves are placed in a manifold, they are easier to maintain. Blowing out your lines sounds like b.s. to me. Each spring, just remove the end heads and fire that mother up. Have the contractor install drains in the low points and lay the pipes 12" deep and forget about freezing. Just turn off the master shut off valve to the system for the winter, and the system drains itself. (you can get either brass drains or "King" drains that are plastic, cheap either way.)
Good luck.
Good luck!