We all know that one setting will always be harder as it can never be balanced but it is waaay too early to start theorising about which one is hardest (from wowprogress numbers) simply because the sample pool is way too low. Currently there is no way to tell which is the harder mode unless you go and try them both in similar gear.

Theres many factors that wowprogress doesnt take into account such as player skill, in the past there have been a lot more first 25 man kills because the top 25 man guilds are 10 times more hardcore than the top 10 man guilds. Paragon proved that brilliantly, this is the very first time a truly hardcore 10 man guild exist (in EU+US atleast) and it is showing already.