>Hi All,
>
>Our company will develop IOS applications. Which Apple notebook at least you advice me? 11", 13" or 15.4" screens, what about ram is 4 GB enough? 64GB SSD airbook would be enough or need I at least 500GB HDD?

One other thing to consider:
You can run windows and windows apps using vmware fusion or other solutions.
Fusion works great, and I can open windows in "Unity" mode - meaning the windows desktop is not visible.
If you might need that, know that VMs are greedy for RAM and disk.

I have a 17" macbook pro, I don't think that size is made any more - it is a beast to carry around.
I ran with 8gb at first, and that worked fine for iOS development and maybe one windows vm running.
I upgraded it to 16gb and it runs several windows and linux vms without complaint.

I would get 8gb as a minimum.
With an airbook, the RAM is soldered on, so no upgrades later.

The 64GB macbook air that I played with in the store seemed pretty full already with just the OS and default apps.
I think the performance difference with an SSD is worth putting up with higher cost and less space.
So, the storage boils down to your budget.
I got a 500GB SSD in my macbook and even after a few years, there is plenty of room.
Expensive room, but plentiful.
I just looked, and there is 120gb used on the SSD and 80GB used on the second hard drive.

If budget is tight, I would get 128GB SSD as a minimum, but expect to do some juggling with an external drive.
If budget allows, 256GB SSD should be a lot less painful.

My buddy who just bought a 15" macbook (not air) loves the retina screen.

Good luck!