I have recently done an experiment of Rollei vs Leica.
Lens: Rollei Tessar (40mm f3.5) on a Rollei 35 and a Leica Summicron 40mm f2 on a Leica M6.
Film: Fujifilm Neopan 400 – the extinguishing black and white film
<Which one is taken by Leica? See my Twitter.>
Let me know which one you like better.