It's kinda hard to use the word reliable in the same sentence as any X product designation as they are all built to similar standards. What kind of reliability are you accustomed to? If you are used to Lexus reliability then you are going to be in for a big surprise after your purchase. If this is not your first X then you can expect the same reliability (or lack thereof) as your previous X(s). I don't think it matters too much what powertrain you get as they all have plenty of known quirks. Regardless of which one you did choose, just make sure you've got plenty of reserve $'s because you're going to need it. Good luck with your venture.

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2010 Lexus RX350 still new
2003 BMW X5 3.0i w/sport package w/68K miles. (gone Thank God!)
2002 Dodge Ram 2500 4X4 cummins diesel w/198K miles, custom repo truck
2009 Scion tC w/46K miles
2007 Suzuki SV650 custom streetfighter
2000 Lexus GS400 w/165K miles