RE: Ports on the Netgear. There is a setting for a SUA Server, which, basically allows ALL ports to be directed to 1 computer.
RE: Why SMC is better for starting out: Has everything the netgear has plus, print server, port ranging, and a serial connection for using a dialup provider.
Now, the Print server is not all that impressive (IMHO). You can't use USB Printers w/o some kind of adapter (if that). Bi-Directional Communication is out (so no messages back from printer about ink status, job status, etc. Besides, you could always connect a printer to one of your PC's and share it out from there. This feature only allows you to save power by running the printer server on the router.
The Port Ranging: Programs such as NetMeeting +Video Conferencing require certain ports to be open, dynamically in fact... and much more than the 12 that are available in Netgear. You can specify to open ports 4000-4300 in one rule. (You could only open 12 of those ports on the netgear).
You can get around this limitation on the netgear... you'll have to read up on it to learn the details.
Games are another concern, some games require dynamic ports in certain ranges to be available or require a lot of ports (again more than 12) to be available. On the netgear you open your machine to attack by putting it outside the firewall (via the SUA Server option). On the SMC you can open only what port ranges are necessary. A little more security...
The SMC having a Serial Port means when your DSL or CABLE goes down you could have the SMC Dial into (w/ a modem) an ISP and still share your network. Saves you from having to mess around when service outtages occur.
Again, the 2 products (SMC Barricade and Netgear RT31x) are both highly rated and you can't go wrong with either. Just decide if the features above are important enough to pay the extra price for the SMC(for me they were not-I bought the Netgear, but, they would be nice to have).
I've only skimmed the surface, you should read the reviews and visit the forums on PracticallyNetworked or DSLReports for the product(s) you are interested in. You will find all your answers and more there! Links are in the history of this thread.