You can read my posts, and Zeekeys too. I think theres a few others that swing the F70. You can get a dime at 8" if the conditions and set up are right, but most of your finds will be 6" and up for targets of the coinage specie...I of course love mine, 4AA batteries last along time, its light and fast, it will be two years April since I got it, and its been with me all over the country ever since.
Make sure you get the 11"dd and get a 5"dd too if you have the money, If this is your first detector, (as it was for me) you will be more than satisfied. I cant think of a "con" with the three you mentioned.
I use mine for Park and School hunting and some wading, and by cracky, it can definitely hold its own there and then some! Heres a picture of a ring and a necklace I found 3 months after I got it...mind you, I didn't know what I was doing, the necklace was on the beach, and the ring was at a park, same day, sold the necklace for 800 bucks and that was when gold was 1230.00
Hang out here a little and read the posts, you will figure out which one will suit you, but dont dink around too long, any of your choices will find you some loot, you just gotta get one and get outside! Theres no gold laying around in the living room!
Mud.