Is Linux Armory more stable than Ubuntu Armory?

With which OS is the cold storage more effective?

I am confused as to how to download the bitcoin qt client for my ubuntu distro.  Can someone lend some advice?

What is the best Dogecoin wallet for down for Linux and OS?

How stable is the Mac OS version of Armory?

If I wanted to set up an offline wallet, and I need to assign a "watching-only" wallet on a computer that already has a wallet, how do I change it?

Once that is done, how do I remove the key data from the watching only wallet once it is converted (assuming the old wallet had key data on it)?

Why are the Mt. Gox BTC values so much higher than other exchanges?  Is anyone paying that price?

Hello-
I am would like a little advice regarding how to back up a qt wallet on a mac using a thumb drive or external drive
My understanding is that I create a wallet.dat file using the "back up wallet" function on bitcoin-qt and then save it to the external drive.
Then, am I to erase the info on the computer's wallet so that the data only exists on the external drive?
If so, then how am I to transfer the data back to the computer's wallet in order to move the bitcoin?
Any advice would be appreciated.
Thanks