For sure the safe deposit box is the right choice if you want to store the btc for a long long time but if you trade them that would be uncomfortable to keep bumping into the bank branch or whatever the safe box is kept, but if you sell and buy btc all day long i think Armory client is the best with an offline pc or laptop or even the bitcoin client will do the job as long as your pc/laptop stays out of viruses range. ( even if you pc will be hacked i think its a low chance the 3th party will be able to sell all your btc at once )
2 days ago i was a newbie with btc trading keeping etc but i try every client and exchange so far and as far as i seen a simple backup of your wallet on external flash drive or email draft will do the job. i'm not paranoia but a simple msconfig - startup or services at every startup will keep you away from having your btc disappear
