I would always recommeded a PPI.
If you need the room, go for it. E39 is more nimble and of course better mpg. My wife drive the E53 and it's also the family car of choice. The E39 is my DD.

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00 E39 DINAN S1 //M5 (82k miles)
06 E53 DINAN 4.8iS, born 2/18/2006 (126k miles) http://www.xoutpost.com/bmw-sav-foru...s-my-dslr.html
90 Straman Z32 TwinTurbo Convertible, (1 of 44 ever made) 5 speed, 444rwhp/451rwtq
01 360 Novitec Spider F1 (26k miles)