[AaronBrown]

I assume you mean that you have a hand that has some chance of winning, but it's less than 50%, and that you will fold if you are raised. Therefore, you bet in hopes of inducing the other players to fold. If they call, you have only a small chance of winning. If you don't bet, you will check, and fold if someone else bets.

People are more likely to call you in a large pot, which makes it less attractive to bet. On the other hand, they're likely to call you with weaker hands, which makes it more attractive to bet. Plus you win more when you win. Another consideration is with a large pot, it's less likely that the other players will check. On balance, I think the bet is better with a large pot.

With two players your bet will get more respect. The middle player may fold with a pretty good hand, afraid that her hand could lose to one or the other remaining hands, and that the two hands might reraise each other. The last hand might fold because your raise into two hands shows extra strength. The check is much less likely to work against both players. Therefore, on balance, I prefer to raise with two other players versus one.

My assumptions may not be exactly what you meant by the question, and of course there are many other variables that affect your decision.