Many players don't really know the differences between cash game play and tournament play. Today I'm going to talk about some observations I have made that may help a player deciding on which to focus on.
The obvious difference is that in a tournament you cannot rebuy. You must always be aware that on any hand (in NL) you can lose all of your chips. This will cause you to play very cautious at certain points, as sometimes it is simply not worth taking a risk on losing your chips, even if you think you are a favorite. An example of this is early in the tournament when you are holding AK. There are certain players that will push all in with a wide variety of hands just because they have watched the WPT and think this is how you should play (this IS how you should play at some points, but only late in a tournament and if you are short stacked). You know that when this player pushes in for a huge reraise, he probably has a pocket pair, and maybe has AK, AQ, or even AJ. Your call is most likely +EV due to the fact that there is probably a 15-20% chance he has Ax, and the other hands are just about 50/50. However, this is not a call you can make. It's just not worth risking going broke as you can pick a better spot to take advantage of this player later (IE when you have AK and see a flop, and he goes all in when you flop an Ace..here you are most likely at least 75% to win). This is an obvious point to many players, but it illustrates the fact that in tournaments you have to play much more cautiously. In a cash game, you would probably make this call depending on the other player. First of all, if a player goes all in like this for a huge reraise, he probably doesn't have AA or KK because he would usually try to milk it for more money. Second, a player willing to make an enormous raise in relation to the pot usually doesn't grasp the way to play in a cash game (aka has watched the WPT like the previous tourney player). We can deduce that if they are this type of player, there is a wide variety of hands they could be reraising with.. a few of which AK totally dominates (Ax), some which AK is a pretty large favorite over (JsTs, etc), and some in which AK is almost a coinflip (pocket pairs), add this all up and we can see that this call is +EV in this situation. Let me reiterate that this is against a weak player....if a known tough player makes this move i would think very hard about calling with AK, and most likely fold. These examples show just how different you can play the same hand in a tourney/cash game. It should also be noted that if you are playing with a short bankroll in a cash game, this call with AK would not be recommended. Although it is a +EV play, the variance that comes along with it is very high. You might lose 8 or 9/10 of these, before winning a bunch in a row. If you are on a short bankroll, you would need to pick a better spot (note: see how important a large bankroll is?).
The big difference in the way i play in cash games and tourneys is the type of pots i like to play. In cash games, i'm usually trying to build the pot as big as possible, because i feel i can make the best decisions and want to get as much money into a pot (that is, when i WANT a lot of money in the pot) as i can. In a tournament, I'm much more cautious. Even though i still have total confidence in my abilities of outplaying the other player, I don't like to play unreasonably big pots because of the fact that one bad card and i can get broke.
Here is an example of how i would play a big hand differently in cash game and a tourney. Lets say i have 77 and i rasied preflop. If the flop came down 723 and i was playing a cash game, there is a VERY high probability that i will make a pot sized bet on the flop. I want them to think I am trying to buy this pot (as i often do). There are many players who will call with ace high here, because often times it is the best hand. And on the turn, i will usually fire out with a pot sized bet too (sometimes i will slow down, or even check, just to stay deceptive). The point is i don't care if i scare the people out of the pot, my style of play is very aggressive and i know that eventaully a player is going to catch a small piece of the flop and decide that i am probably bluffing. They may even raise me with nothing, in which case i will probably slowplay the rest of the way inducing a bluff. The point is, it is very rare i will slowplay in this situation even with the nuts, as it just is too hard to build a big pot and it gives them chances to beat you.
In a tourney, i would play this hand diferently probably. Since I am playing tighter in a tourney, i will see less flops and have less chances to make big hands. When i get a hand, i need to maximize the value of it. Even though i could win the biggest pot possible if i bet pot and get called, i will either bet less than the pot or check with this hand, so that i can almost always get something out of the other player. The reason for this is because of the nature of tournaments themselves. If the player has a mediocre hand after the flop, he would probably fold to a large bet because he is worried about losing his chips. If i make a bet that is half the pot, or check, he will probably be sucked in because he thinks he has the best hand. I can continue to bet bigger and bigger as the hand progresses, in order to get the best value for my hand. Now, if i am playing against a tough player, i may be more apt to bet larger because he may view this as a bluff or may want to make a play on me.
To summarize, when you are playing cash games there is rarely a reason to slowplay even a monster. You shouldn't be afraid of going broke, so you should be aggressive most of the time. This should carry over to your monster hands as well. In a tournament, you are afraid of going broke, and you won't have as many chances to get monster hands so you should try to maximize their value, even if it might cost you a little bit in EV.