A micron rating is given to show the efficiency of the oil filter (one micron is a millionth of a meter).
This leads consumers to believe that the 10 micron filter must be better for their bike. Here is where it can get confusing; though the 10 micron filter may have a higher filtration rating it does not allow the oil to return to the tank as fast. With this in mind, the 10 micron filter was developed for use with the Twin Cam style engine, which has a different oiling system that allows oil to be forced through a more restrictive oil filter. The reason for the tighter filtration was explained by the manufacture as necessary to assure all of the smaller passages, in the Twin Cam style engine, would stay clear of debris. If you run the 10 micron filter with an evolution style engine it will not be able to return oil through the filter fast enough causing the oil to back up into the lower end robbing power and/or causing oil to puke out of the lower end.
The 30 micron filter is designed to work best for your Evolution style engine, the filtration is still excellent and it will not cause oiling issues.
When it comes to filtering oil application is very important. There have been a lot of changes and updates too many filters on the market, with claims of better filtration, don't be fooled into using a filter that might not be the best for your bike.