@hasmunfx, James highlights an important point above.
When people talk about their leverage, they sometimes mean the leverage they are using per trade AKA their effective leverage, and they sometimes mean the maximum leverage available to them in their account. You sometimes have to figure this out from the context.
When someone says they use 10:1 leverage, they're probably referring to their effective leverage, the amount they use per trade is 10:1. That means, the size of their open positions is 10 times the amount of money they have in their account.
When someone says they use 400:1 leverage, they're probably referring to the maximum leverage available in their account, because it's unlikely their open positions are 400 times the amount of money in their account.
Leverage magnifies gains and losses, so it's important to manage your risk appropriately. Speaking of risk management, you might want to approach this question from a different angle. Instead of trying to pick the best leverage, try to choose the best trade size.
For example, many traders talk about limiting your risk per trade to 2% of your balance. This is a good place to start. Suppose you have $8,000 in your trading account. You can then risk $160 per trade. Suppose further that you identify a trade opportunity on EUR/USD and want to set your stop 40 pips away.
With $160 to risk on 40 pips, you can risk $4 per pip on this EUR/USD trade. That equates to a trade size of 40K EUR/USD or 4 mini lots. Incidentally, that's approximately 5:1 leverage on your 8K account balance. It's only approximate, because 40,000 euros is more than 40,000 US dollars, and the account balance in our example is USD.