Drive both and see what your feelings are. I sold a 540ia for a 740i sport and have driven the 540i sport. Aside from the manual transmission thing (great fun, but not every day) I find the 540 does all the things I want in a car better (ie is quicker, more agile, and better handling) but the 740 is more satisfying. It is an inexplicable feeling that can only be determined by driving the cars. There isn't a day that goes by on my way to work that I don't say to myself, "I love this car!".