Agreed,it should be plenty. (er-x-sfp here)
I believe the main differences are:
ERX
- Faster cpu
- hardware switch
- less hardware offloading. Originally there was no offloading, but that has changed. I can't remember if there's 100% parity, though the X offloads hwnat and ipsec.
Lite:
- more memory
- more storage
- ultimately faster with more bandwidth capacity. Though I don't believe most of us at home will need that. (* except ya'll with the 500mbps-1gbps fiber...)
.. If you're looking to do anything like add debian packages or use squid/webproxy, then the X might be too lightweight.