My dad either had the choice of an E39 or E60. Went for the E60 and didn't regret it. Looks a lot more modern imo and feels a lot bigger inside with more space and just overall a much nicer more modern car. If you want the best of both worlds get a E60 M5...

Like I said if you are looking for a diesel E60 525d or 530d would be very nice imo and similarly with petrol 525i or 530i. Also depends whether you want an M-Sport or SE.

As for a 16mpg 530d that is a pile of cack....there is something SERIOUSLY wrong with that car. No way is it performing like it should be.