I have Michilins on the X5 now but will switch to Contis (DWS) as soon as the Mich's are worn a bit more. I've used Contis on my e53 for 4 years and they perform well in all respects, plus they really are great in snow (even deep snow).

For the OP, the answer depends in part on whether you need snows/winters, can get by with all seasons (as I can), or live the luxurious life of summer tires year-round. No matter the tire options, I never scrimp on tires or brakes, two areas where a few bucks saved could result in a serious accident. I don't run my tires down to the wear bars, I run them until they start to lose grip in the wet at normal speeds on my drive - this is always a bit more tread than the wear bars for me. So I don't buy used tires anywhere except in an emergency, and those get replaced asap. Others may be more expert in evaluating a used tire, or willing to take more risk.

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Mike

2005 e53 X5 4.8is 169k miles
2018 f90 M5
2018 Volvo XC60