Ask 7 more people and you will end up with a total of 10 different answers!
From the longevity of the engine point of view, more oil is better. From the environment and cost point of view, less oil is better. You will find slight variations in mix ratios based on the measuring system: i.e., in lites you would round off to 25:1 where as measuring in gallons & ounces you would end up at 24:1
Years ago the standard mix was around 24:1. With the introduction of synthetic oils the same level of lubrication could be achieved with a much less volume so the standard mix crept up to 40:1, 50:1 and even in some cases 100:1
My recommendation is to pick a mix that you are comfortable with and then stick with it. The oil doesn't really count as fuel when it is burned so changing the oil to gas mix will also change the fuel to air mix in the carburetor. Ideally, you will adjust the jetting for the oil mix you are using and then you won't want to change oil mix unless you intend to rejet the carburetor. If you are riding the bike really hard, as in racing, then you might want to run more oil, such as 25:1. If you trail ride a lot and don't push the engine hard at all then you might want to use a higher ratio, such as 50:1 so that you don't foul the plug as easily.
Rod