If it is a vehicle just for you to drive and no need to carry kids around, I would go for the M3, but with a family definitly the X5. Go with what suites your needs, but if I had no kids M3 for me no question or hesitation. Have you considered the M5?

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Sasakyan Kita
'96 E36 / '02 E53 Sold / '07 E70