The one on the left - Baaahd. The one on the right - Gooohd. At least on a 10V. The slightly smaller tip is often recommended for the 20Vs because it reduces parasitic sparking to neighbouring cylinders.
The centrifugal weight (no nit-picking about centripetal) will limit rpm before the ECU. This can actually be useful if someone has jumpered the fuel pump so that the ECU cannot cut it if it detects overboost - a rotor arm like this will then protect the engine against over-revving.
In like vein - a fuel pump relay with "Kraftstoffpumpenrelais mit Drehzahlbregrenzung" has a similar effect. These relays are standard in many Audi non-turbo I4s of the 1970 and 1980s, including the Coupé GT and Coupé quattro - they must not be used in ur-quattros. Three found far.
This one's just taking the piss.
The incredible thing was that the car ran. I pointed out the detrimental effect to the (selling) owner and he got quite narky - "Put it back and don't touch anything else." Then I sat in on a test drive, with said owner saying to potential purchaser: "All these cars are a bit gutless above 5,000 rpm". The new owner got another 15mph on the top speed for £3.15 at Halfords
A car like this is a great deal for the buyer - a rotor arm like this (or indeed any other manifestation of limp home mode) suggests strongly that the engine hasn't been thrashed, and a significant performance boost is available at very low cost.