It is well known that I am extremly bias on this topic, so take what I say with a pinch of salt.
This is a no brainer, E65 FTMFW !!!!!!!!!
The E65 is a superior car to the E46 in every way, and there is a fair chance it may outhandle the E46, uhuh, you read correctly, the 7 series boat will handle better then a E46...
However, some precations, the maintance on the E46 vs the E65 is worlds apart.
If you buy an E65, follow the simple guidelines.
Has to be manufactured 2004/3 and above, try and go for a facelist which was 2005 and above.
While the N62 motors are brilliant, and the most common/best value for money is the N62B45 ie the 745, and parts are fairly available, its still expensive to maintain.
May I suggest the 730d, its the same M57N motor as is in the 330d, 530d, ect and those motors are bullet proof if you treat them correctly. Also have a combined fuel consumption of between 9l/100 to about 11, mine gave me straight 10 all day every day, does not matter my driving style, ie, peddle on or off.
The common problem is electrics, which is why you want the 2004+, the fibre optic cables in the doors do break, the gearboxes may be problematic.
There are chawk and cheese cars, cannot compare, and if you buy the RIGHT E65, you will not be sorry.
E65's are also traditionally in better shape then their 3 series brothers, and can be had for the equiv of packet of chips.... so its exceptional value for money....
I will own another E65 in the very near future, patience my pretties, patience...