Garden fence posts - treated round or square 4x4's? And fencing?

Question:I'm putting up a 24' by 70' garden fence. I have a choice between round 10 foot posts or square 4x4's. Which is better? Or is there something else to look at?
Also fencing, I am thinking 5 foot field fencing with 1"x2" spaces and then single wire above that every 10 inches with blue marking tape tied to it. We have lots of deer, rabbits and other critters. What spacing between posts can I get away with for this type of fencing? I am thinking 15 feet.
Thanks

Answers:
Most round posts are peeler cores which tend to warp a little more than 4X4's. They both work pretty well. I am not certain about spacing from your description of the type of fence, but it seems a little far. Unless you get a lot of tension on the wires it seems they will sag. Most fence post spacing is more like 8 to 10 ft.