Think of it this way. If you have an avg 2 pip comish+spread+slip....... on a 25 pip stop you need to make 8% a year just to break even. The wider your stop the less house vig has an impact on your bottom line. If you have 2 pips of costs per trade and use a 50 pip stop then you have to make 4% a year to break even. 100 pip stop , you need to make 2% to break even ect.
If you are taking a trade that has a 1:1 risk reward expectancy whether it is risk 25 pips to make 25 pips or risk 50 pips to make 50 pips your odds of winning are still 50-50 minus commission , spread, slip.