Originally Posted by tmv

^E36 and E39 are pretty much the same as your E53. Of course, you would save on gas since they are smaller and lighter.
The engine is the same, even with the smaller displacement M54B25. They share lots of components --> same ups and downs. Still need the suspension overhaul, cooling system overhaul. Same maintenance on Vanos seals, DISA valve....
If you have your E53 in good maintained condition, I'd say keep it.