Using the counter for each ISO I created the following table showing each Ubuntu flavour as a percentage of the total downloads for recent releases:
Initially I thought the results might be slightly skewed as Ubuntu has always been provided first before the other flavours. However as the total number of downloads is large for both releases I don't think this has caused any statistical anomaly.
I'm currently using these counter statistics to decide the priority for uploading new releases. So if you were wondering what happened to the 16.04.2 Kubuntu ISO now you know.