In terms of what you get out of it, nothing's different. The only difference being that the online code is emailed to you immediately after purchase, and the card (which contains the code) is shipped to your house.
Sometimes when you download a code or try to, the authorization system messes up, locks up your credit and you have to spend hours proving who you are to get the code released. The card is a sure thing and $35 today vs. 40 for the code.
I know its a bit late answering your question, but whenever you see xbox live 12 months for under 35 or 40 dollars, just go ahead and buy it if you want. live subscriptions stack. I saw a sale for live for 33 on ebay and bought one. I also got another one for 35 from my cousin. i'm basically set until January 2015.