m8 if he can afford it ...go the crd Grand....my boys are 14 and 16 and a little taller than my 173cm already...they fit in extremely comfortably and we all like it better than the 80GXL we had. Mind you it's a very personal thing. I suggest he goes for a test drive to see if it's for him. There may be something he doesn't like, who knows until he drives one.
I've gotta admit it was a brochure on the ML270 that Merc sent to me that got me interested in the crd and when I found out the Grand had the same running gear and MORE features for $25,000 less I could'nt wait to take the Grand for a test.
After driving it for the first time I just HAD to have it.
But only your mate will know what suits his tastes and situation.