Just ride what you like and feels good. Riser bars feel different than flat, and personally I like them. I like the handling, and as it takes some of your weight of the front of the bike by putting you in a more upright position, it becomes easier to pop the tire over roots and rocks while maintaining a balanced riding position. You also get good leverage on climbs to make up for the lack of bar ends.
As for the stem, 5 degrees isn't a lot, and you can use a 5 degree rise stem with risers too. I do.
What Kona is it?