I wrote a small test, comparing the performance of case sensitive and case insensitive hashtables in .NET. The result is, that the case sensitive hastable is 3 times faster than the case insensitive hashtable …mmmh, quite a difference!
Case sensitive – 527 ms:
new Dictionary<string, string>()
Case insensitive – 1297 ms:
new Dictionary<string, string>(StringComparer.InvariantCultureIgnoreCase)