Akan vs. Shikotsu (Hokkaido)

Does anyone have any advice on choosing between Akan NP and Shikotsu NP? I view them as somewhat similar in the sense that I would like to do some hiking in an area with lakes and volcanic mountains. It seems there is a nice hike on Meakan-dake from Onneto in Akan NP and also a nice hike on Tarumae-zan from Shikotsu-ko. Right now I have a preference for Akan because otherwise I probably won't go to Eastern Hokkaido, but in the Japan Roughguide book they don't give Akan a very good review (they even specifically mention Shikotsu as being better). One thing that might tip the scale for me is if I don't need a car in Shikotsu, whereas that seems necessary for Akan. Also, I was thinking of heading to Akan from the Asahikawa area by train. Would it be better to go around north and get a car from Abashiri or to go around south and get a car in Kushiro? I am leaning towards Kushiro since that seems like it might be more scenic (going through the Biei/Furano area and also the Kushiro area). One more question, I read that Meakan-dake can sometimes be closed to hikers due to sulphur emissions: is this very common or likely?
Thanks in advance for any input!

I have been around Shikotsuko including some hiking, and I have been to Akan, where I did not hike. I enjoyed both. And I recommend a rental car for both.

I think a major factor would be access. Shikotsuko is just outside Sapporo, while Akan is on the other side of the island. Very time consuming to access from Sapporo. Depending on the rest of your schedule, that might be a major consideration.