The 6 is definitely bigger but my previous 2011 535 xdrive M compared to my 2014 640 xdrive M is quite similar in ride and performance. If anything, the 2014 inline 6 turbo is more responsive. A welcome upgrade. I can't speak for a 2015 5 series. I was very happy with my 5 and even more happy with my 6. Just go and drive them
