Hello,
I have a 15" black leather on black 3 spoke MOMO and I love it. My coupe came with a smaller (14"?) wood and chrome unit and it seemed too small for the car. Also, the wood hoop's color was a different tone (more blonde) from the the rest of the car's wood. Smaller wheels just look 'small' in the E9 cockpit, but just fine in a '02. Its ust a scale/aesthetic issue personnally, ultimately a pilot/owner prefernce.
Depending on what your going for, appearance or function, a dressy/formal or more athletic look, should influence your choice. Wood wheels are beautiful & elegant, leather wraps offer more grip/support for sporting situations. If creating a show car, either the Petri CSL wheels (chrome spokes) or a 3 or 4 spoke MOMO/Alpina (black spokes) are a good aftermarket/period, sport choice. Lovely Nardi's will definitely dress/polish things up. Again its pilot preference. If the car ever sees the track, a leather wrap is the way to go.
No affiliation but, there is a german Ebay seller (Krull??) that has some great wheels from time to time. I got mine from him and it was a smooth deal.
HTH and good luck
-shanon