I'd like to secure my bitcoin with an offline wallet. A lot of security conscious people seem to use Armory. I am trying to get a better understanding of the differences between these two clients.
I plan on having a cheap netbook, never touched the internet, and using it as an air gapped offline wallet. If I need to make transfers then use a USB to sign transactions for the online wallet.
Electrum is easier. Armory is harder. Electrum lean towards minimalism. Armory is aimed at power users.
Even though you asked about offline wallets you will likely want to maintain a watch only version of your wallet on your online system to be able to see the current balance, create unsigned transactions and give out addresses to people who want to send you money. So let's compare the online wallet experiences as well.
Armory's online wallet requires a copy of bitcoin-qt running and that means you need to download the whole blockchain. Armory's online wallet is also known for being a memory hog. The advantage is that you have a local copy of the blockchain and don't have to trust anybody else with that.
Electrum relies on third party servers so it runs pretty lean. The downside is that you loose out on privacy to those servers and if they are compromised they could send you fake transaction data and not broadcast your send transactions. They can't steal your coins though - your private key is never shared with them.
BTW if your netbook has wifi then make sure you turn that off in the BIOS.
Electrum lets you manage offline wallets and still safely spend from an online computer.
You don't even need to use an insecure USB key, you can use webcams to make the computers talk to each other.
See these instructions for more information http://electrum.org/tutorials.html#offline-mpk
Since you just need to create a password-protected wallet file, most Bitcoin clients offer this functionality. Electrum uses a third-party to download the blockchain, so perhaps just for that reason I'd rather go with Armory. Certainly has a lot more security features. But again, since all you need is your password-protected wallet file you can also use MultiBit.
I also use a laptop for this. I make sure it's disconnected from the internet. I run MultiBit on it. Create the password-protected wallet. I can then deposit in this address my savings. When I need to retrieve my funds, I connect it to the internet and run the transfer. Make sure you're using Linux.
Electrum is definitely the best general public bitcoin wallet ever made. Downloading GB of blockchain is not an option for many users. Electrum is very secure. It can be used on offline computer
