What is the best URL for dashboards? What is the most common and what users remember the best?
go.site.com on.site.com dashboard.site.com app.dashboard.com
PS I hope url naming is part of UX
You should probably do some AB testing to see which sticks best.
One thing that I believe will have an impact is how who your user base is. Most non-tech people I know would try site.com/dashboard first because they aren't as used to subdomains, while people who do work in tech tend to go for dashboard.site.com
The best solution would probably be to use multiple different ways at once. Google and many other companies do this. (maps.google.com redirects to google.com/maps for example)