I'll just post up what I did on the the F10 board post, lol.:
I absolutely loved the F30 328i when I drove it. Thought it felt like the best "Small Sport Sedan" I've ever driven.
IMO the relationship between the F10 and F30 is great, at least if you're someone who is okay with BMW's move to more luxurious endeavors. The 3 has refined up a bit, but is noticeable less "occasional", less elegant and sophisticated, less curvaceous as the 5. It's a little more angular, squared, and has a more fussy "immature" nose, which is appropriate for it in relation to the 5.
The interior of the 3 is nice, but when you go from it into a 5, you instantly feel the extra airiness, the much more expensive, "sense of occasion" atmosphere, the plusher experience, etc. Again, appropriate between the two (purist buyers of each might not want the effects of the siblings in their cars).
The F30 feels very lively to me, very fun, though the F10 does as well. I think if you want pure sport with enough luxury to meet ends meet, the F30 is the car for you. If you want an ultimately refined Luxury Car with enough sport to make ends meet, the F10 will do the trick better. Of course, space is another objective factor.
IMO BMW has nailed it with the F30 and F10. And IMO the F10's move to more luxury made more sense once the F30 came out.
'13 F10 BMW 535i Sport
: Jet Black/Black-Anthracite : Premium & Technology Packages/Sport Auto Trans/Camera/Park Distance Control/Heated Seats/Tinted Windows/Blacked Out Markers/Performance Spoiler.
Ex M-B's: '11/'10/'06 E350's w/ AMG Sport Package, '02 S500 w/ Every Option.