I didn't especially like nor dislike the seating position on the C300 and the adjustment of the C300's seat was limited, I like the bottom cushion to be able to be tilted up. The BMW had a better seat position, seat firmness, seat feeling, and non-invasive bolstering; plus I was able to adjust it the way I liked. The C300's seat was aesthetically more attractive.
The BMW did have a problem though, the hole between the steering wheel rim and the airbag wasn't quite big enough for me to see the entire instrument cluster. I couldn't see the very top nor the very bottom of the instrument cluster. So this was a very minor problem with my seating position on the BMW. The C300 didn't have this issue.
I would be happy with the C300's seating position, and it would work for me.