It all depends on what riding position you want. If you want to match your existing handlebar location as closely as possible then the easiest thing to do is to use our +/-6 deg stem in the +6 orientation with one or two extra stem spacers to add back in the rise.
If on the other hand, you are looking for the most upright riding position you can get then we recommend going with the +30 degree stem. The difference in rise (or handlebar height) is not that dramatic but the handlebar will be a bit higher up and the riding position will be more upright.
The image below shows a comparison of a 100 mm length stem in +6, and +30 where the Reach is (X) and the Rise is (Y):
For further questions related to this topic, you can email us directly at firstname.lastname@example.org.