Short stack pros
• There's less risk. If you buy in for $100 in a $1-$2 blinds game, you can't lose more than your initial $100 stake (and any profits you may have gained) on any one hand.
• You can often cause big stacks to make bad decisions. Bigger stacks in no-limit games often think of the small stacks as just a nuisance. I've played with a short stack in an online game and been called a "gnat." As a result, big stacks will often make calls with questionable hands if you push all in. I've seen pot sized calls with queen high and nine high before. So if you get A-K, A-Q, 10-10, etc., try re-raising all in against a big stack.
• The not so aggressive big and medium stacks may not want to tangle with you while holding mediocre hands because of the threat of you going all in on them. They are apt to believe you are pot committed when you really aren't, which allows you to pick up some pots uncontested.
Short stack cons
• You have less to gain. If you buy in for that $100, that's all you can win if you double up. Had you bought in for more you may have been paid more on your winning hand. For example, if you were up against a player with $200 you could have won double what you actually profited when you beat him.
• The big stacks will often bully you relentlessly. Unless you pick up a decent hand, the blinds can eat you alive as you make fold after fold. Being short-stacked in a cash game can be similar to being short in a tournament in that sometimes you may have to just pick a hand and make a stand. If you think it's silly to do that in a cash game you should pick your chips and leave because it does no good to let the blinds take your stack.
Big stack pros
• You can win more. The greater your buy in, the more you can win if you double up.
• The big stack allows you to bully others. Medium stacks and other big stacks will be less likely to tangle with you because you can bust them. Raises and continuation bets on the flop often take the pot. If another big stack is aggressive against you when he is usually more docile, you can be pretty sure he has a big hand and you can escape without further damage.
• You can lose chips on one hand and still catch back up on a future hand. If you buy in for a high amount and lose some of them, you can still double up later and end up where you started in chip count. The big stack gives you more leeway in this regard.
Big stack cons
• The risk is great. If you put all of your chips into the pot and lose, your financial downfall is greater.
• Other big stacks can put pressure on you. If you face a sizable bet from another big stack, you risk going broke. If another big stack perceives you as a player who is afraid to lose his buy in, you are really vulnerable to his aggressive tendencies.
• Many players feel invincible with their big stack and put their money into the pot in questionable situations. (See the ten high reference above.) If you buy in for a large amount, play your stack wisely.
Which method should you use? Both have their talking points. The choice is up to you. PokerWorks forum is a great place to discuss and learn.