I just found some information on this machine on the internet. Apparently it is a mostly steel machine, but it does have some nylon gears, which makes it vulnerable to wearing out. If the gears wear down, it is more expensive to fix/replace them than the machine is worth. The previous model, 337, had all steel gears, so it would be a better choice.
This is kind of your call. How much do you love it? :-)