Drive them both...
We test drove the 28i first and thought it was great. Then we drove the 35i and decided it was perfect.
The extra power and smoothness of the turbo six is just a better match of the weight/size of the X3 in my opinion. I also highly recommend the M-Sport package as well.
Last edited by leewtech; 10-08-2012 at 10:28 AM.