I was going to keep out of this one and just smile
But It all depends on which 156 and which 166.
As far as the 156 is concerned, well having owned three different types a 2.0TS, a 2.4 JTD 10v and now a 2.5 V6 24v as well as driving on a regular basis family owned 1.6TS, 1.8TS and 1.9 16v JTD..... All I can tell you is that there is a strange obvious familiarity to them all yet they also drive and handle completely differently... Not talking just the engine and power outputs but the balance and feel and they way they deliver it... None of them are bad, just different.
I don't know how the hell Alfa did it but they managed to make all six different variants of the same car almost like another model in the Alfa range...
IMO a 2.0TS Veloce sp2 is by far the best handling and best balanced of them all and sorry but the 166's I have driven (a 2.0TS Lusso and 3.0V6 lusso) wouldn't be able to get anywhere near when it comes to the twisty stuff...
The handling of a 2.0 TS is thought controlled, you are that plugged in, on a perfect bit of road kissing the apex perfectly without a grumble or complaint... If a 156 understeers, you aren't going fast enough and doing something wrong... They can suprise and lift off oversteer once the the limit is rarely passed but easily brought in line!
Best fun though?... A V6 24v everytime
The 166 is a beautiful powerhouse of a cruiser that can surprise too