[Geary]

I think the earlier BMWs also had the Porsche-patented synchro.

The second gear synchro does indeed have a harder job to perform (and gets worn more quickly due to lots of downshifting action) because the idler gear is physically larger/heavier than 3rd and up. More weight = harder to synchronize. This is why it's good from a manufacturing standpoint to remove as much weight as possible from large diameter idler gears. (GT-brand 915 gears are right around 15% lighter than comparable "drilled" gears, because they are side-profiled for weight reduction.)