Travel in Tokyo - JR or Suica?

I will be in tokyo for 8 days in April (this is my first time) and my travel plans are strictly withing Tokyo city. which is cost effective and comfortable? The JR Pass or the Suica cards?
Thank You!

Suica cards. The Japan Rail Pass only makes sense if you make long-distance trips.

Uji is correct, but I just wanted to give you a little extra info.

You don't actually require a Suica at all. You can purchase individual tickets or a day-ticket with cash.

Suica does not reduce the cost of travel at all, it just makes it convenient not to have to buy tickets.

A Day-ticket on the Tokyo Metro does not cover travel on the Toei Subway, so if you wish to switch lines you will still need to buy a ticket for the Toei portion of your journey.

If you are flying in to Narita and wish to take the Narita Express in to Tokyo, you can buy a combined "Suica+N'Ex" ticket, which includes your Narita Express trip along with a tourist-only Suica card (it has a pretty picture on it which isn't available to locals).

If cost is your main priority, I'd take a slower train than the N'Ex and just buy individual tickets or day passes - day passes DO save you money if you take about 4 journeys in a single day and stay on the network you purchased it for.

I hope that helps :)

Hello, i'd like to ask if suica can be used in Osaka too. Thank you.

If I recall correctly, as of two days ago you can use the SUICA in Osaka.

Suica has been valid on JR trains in the Osaka area for years. Since Saturday, it is now also valid on non-JR trains, subways and buses in Osaka and surrounding (and several other major cities in Japan):
http://www.japan-guide.com/e/e2359_003.html

Thank you for the correction, Uji!