Suica cards are just pre-paid rail cards. My wife has one she sometimes uses. We also have ICOCA which is the same deal, just a pre-paid card for use at the gates. They are handy and I would get one if you aren't going to get a rail pass. However, if you will do considerable traveling during your visit to Japan I would highly recommend the rail pass as it will save you a lot of money. Just keep in mind its only good on the JR line you choose. You can get a JR Pass that is good on all of the lines as well. More info is available here:
http://www.jtbusa.com/en/jr/j-jr.asp
There are some restrictions on which trains you can take but even with the ordinary coach class, pass you have a wide selection.