I had to laugh at a comparison between Sergeants-Major and Master Gunnery Sergeants (both grade E-9, the highest enlisted grade) in the US Marine Corps. Here are a couple of examples.
MGySgt 3. If you ever find yourself in the MGySgt's office, there is a good chance you'll be able to sit down and talk shop with a ready-made cup of hot Joe and get a strong hand shake on the way out.
SgtMaj 3. If you ever find yourself in the SgtMaj's office, it's very likely you won't be able to sit down at all because of all of the "I love me" stuff and you won't have time for a cup of coffee because you'll be too busy making sure every sentence ends in SgtMaj. On the way out he'll make sure and remind you about your duty on Christmas day.
MGySgt 4. If you run in to the MGySgt at the club, he'll probably be a half-a-beer away from smacking up some lieutenant and about 3 chicken wings away from a heart attack. He'll gladly invite (order) you to come over and drink a beer with him while he tells you how shit hot of a Marine you are (can you drive him home).
SgtMaj 4. If you run in to the SgtMaj at the club, he'll probably be drinking a watered-down Pepsi and eating unsalted popcorn because his body is a temple. He wouldn't think of inviting you over because he is with his fellow 9999s and you just wouldn't understand. On the way out the door he counsels you on saying the f-word too much and reminds you about duty tomorrow.
There are lots more at the link. Three friends (two NCO's, one officer) in the Marine Corps told me (after they stopped laughing) that they thought the comparisons were pretty accurate.