X-5 3.0 or 4.4? new or used?

Hi All, I am looking at buying an X5 and need some input from you owners out there. I test drove the 2005 4.4 version and fell in love, but am wondering if I am better off buying a used one. If so, what years are best? What years do I steer clear of? Which engine is recommended/preferred? Maintenance issues? There appears to be a small difference in gas mileage (not a big factor for me anyway) between the 3.0 and the 4.4. I need a more versatile vehicle these days and my 525i, even though I love it, just isn't doing the job anymore. TIA for any advice, recommendations, etc. Or, should I buy a Touring? Kathy '94 525i