What a ridiculous question!
And only Susana and Fearless have provided any worthwhile conceptual answer.
The correct answer does not live in the number of contracts per trade, period. What's that, your system is based on volatility? Well, throw a few more contracts at it! What's that, your system is based on intraday trends? Well, throw a few more contracts at it! What's that, your system does not use hard stops? Well, throw a few more contracts at it! What's that, your system uses 1pt hard stops? Well, throw a few more contracts at it! Wait a minute, dog days are coming.
The correct answer lies in your ability to recognize change and successfully deploy an appropriate strategy and style of trade, suited to the dynamic nature, intraday and otherwise, of the market. As Susana said... some can do it with 1, some can not do with 100.
Osorico