all of the above advice is wrong but not that wrong.
1) to solo mine you need to run a server with bitcoin-qt that means you need to spend extra power to solo mine
2) if a real pool offered solo mining server like
http://bitsolo.net/ does you no longer need to spend extra power to solo mine
3) So first advice is you need to decide the power cost you will do to solo mine.
Once you figure the power you need to spend to run a real solo mining setup. You need to see what pool fees are from a pool on 12th.
Ie if running your own server costs 50 usd a month and the pool fees on 12th of earnings are 75usd a month for a shared pool.
In the long run solo mining is better Now everyone above is focused on variance and leaving out the facts above.
As for variance risk you can get crushed .
your chance for hitting a block today is 77 to one.
next jump it will go up.
So if you want to solo mine for 12th 1 day on a real server the cost will be the .3221 btc you would have earned mining and the power to run that solo mining server.
Frankly If you know how to set up a server to run the bt-qt in server mode and want to run for 1 day today you are spending 2 or 3 bucks to run the server and you are spending .3221 btc you would have earned in a regular pool.
so you would spend about 200 usd for a 77 to 1 shot at 1 block.
BTW my vote is run solo 1 day a week run pools 6 days a week. I do that here with underclock/undervolted usb sticks as a test study. I can't justify running a pc as a dedicated server for solo so I use bitsolo.net