I am using a Garrett GTI-1500, which is an upgrade from the AT-Pro, except that the Pro is better in the rain. The 1500 can have the coil under water, but the computer box is not waterproof. The 2500 is an upgrade from the 1500. I am very happy with the 1500. I like the weight and balance. Once I began to understand the GTI feature I became successful in using it. I think the Garretts are very user friendly and easy to learn. I believe the 2500 will find things deeper than the others, if that is an issue for you.
I believe all the machines you list are fine and have nothing bad to say about any of them. I have never used a Whites, but understand them to be a quality detector.
1) The best machine is the one you are comfortable with. It needs to balance in your hands.
2) The best machine is the one you practice with and learn. All these machines find things. Once you learn the machine you will be able to tell the difference between the good things and the not so good things.
Knowing you want it for Coin Shooting helps. However, questions remain. Will you use it on a beach in wet sand? Will you want to use it in the rain? Are objects, such as coins, very deep where you hunt?
Good luck with your choice. Whether you stay with the AT-Pro or move on, Practice, Practice, Practice.
Happy Hunting.