I actually ended up returning the 30mm ones as they were a bit big and I found the ochre ones shortly after buying the 30s. I prefer the color of the ochre as I feel it's a bit more versatile. Also, the profile of the classique chelseas was slimmer overall which I preferred.
Re: heel height, I think both 25mm and 30mm are great heights. The 30mm has a bit more of a distinctive look to it but 25mm is very easy to wear. Between the two I'd say heel height was probably one of the least contributing differences and shape was the biggest reason I went with the classique 25mms in the end