BMW 1 series are, in my personal opinion, not a BMW at all. It's more like a VW golf try to disguise as BMW. The build quality of the car just feels ... hmm ... a bit cheap.
Reasons I choose Lexus over BMW,
1. more for your money as Parthiban said :)
2. the steering is lighter (wife likes it very much)
3. reliability. Father’s X5's air con dies in 2 month from new. Uncle’s 10 year-old 5xx was on fire. And I have to have my 325's air con, rear whip, headlight, CD changer etc. fixed.
But to be honest, BMW does offer better driving experience in "some" occasions.