Yes, size is matter, if you have a lot of money, you can use a big lot, and you will get more profit, But be careful with broker you choose, they usually give your account a limitation, for example, you only can open 10 lots maximum or something else, it is annoying right? But it will never happen if you trading with FreshForex, you can choose lot as big as your margin can open it, no limitation, no requte, just trade and get your profit.