Domain elitism gets on my nerves.
Logical does not always equal usable. For the average user, www.domainname.tld is the formula they are used to, anything else confuses them. Why do you think www.mensa.com has had over 750,000 hits? There are those that say all local Mensa groups should have subdomains under the mensa.org domain. But, localgroup.us.mensa.org is long, unwieldy, and very forgetable. No, it doesn't hurt to have the "logical" subdomain redirect to your usable domain, but you should advertise the one that people can remember.
If you do your job correctly, there will be no guessing games. Those familiar with the website will be able to remember the URL. Those who are not will type "Mensa" and the name of their city and/or state into a search engine. You are working to improve your search engine standings, aren't you?
By and large, Mensans are average web users. Highly intelligent, but just as likely to be unfamiliar with the web as the other 98% of the population. At least, that has been my experience. And don't forget that many of your visitors will not be Mensans. You cannot guarantee that visitors have the slightest clue what a logical subdomain is.
When providing a service to people with varying skill levels, simple is better. Simple navigation, simple URLs, simple domain names. Keep it simple, webmaster.