Stumpy is correct, because the length of the side apposite the angle is the same on both methods, if a micro bevel is honed o the steel. An edge straight off the grinder is good enough if you want a lot of slips and like to work your but off. A small bevel does wonders for a cutting edge and one doesn't have to remove much material to freshen up an edge as work progresses. With a flat edge a lot more metal needs to be removed.
It is said that a 25 degree angle is for soft woods and a 30 degree angle is for hard woods. The pattern shop I worked in had their rest set for 27 1/2 degrees because they worked with both soft and hard woods. I was told when in my apprenticeship that 22 1/2 degrees included angle was the prefect cutting angle and since 25 is closer to 22 1/2 than 30 so I sharpen at 25 and not 30.
In reality it makes no difference to me as to how you wish to sharpen. You can do it any way you want, at any angle you want, it is your tool not mine I think Bob Dillan said it best ( don't you understand, it is not my problem).