Depends on what you want. They're both very good vehicles.
BMW will handle/perform better.
Lexus has a much higher quality interior (much more luxurious).
Lexus will have better build quality (slightly).
More user features inside the Lexus.
If it's about performance you may want the V8 the BMW is the only one offering that. And their X will out-handle the Lexus for sure.
Of course Lexus offers the vehicle in a hybrid version that has V-8 like power but it's more expensive than their 6-cylinder.
What are you looking for from this vehicle?