UN-73 BB. The square taper Shimano style. I have noticed these have come with both aluminum and plastic BB cups.
1) Which came first?
2) Is one considered an upgrade or a cost saving move?
3) Do the plastic ones tend to squeek less?
4) Is the plastic as robust (durable) as the aluminum?
The reason I ask is that I recieved one of these today with the plastic cups. First I have seen...
<edit: I do mean the removable cup is plastic. The other is still aluminum.>
Any feedback is greatly appreciated.