Complete JR Pass Noob, Please Help!!

Hi Everyone :)

Myself and my partner are travelling to Japan in February 2015 and will be staying for 2 weeks. We will be landing in Narita and have a hotel booked to stay in Akihabara. My question is:

I have been told my different people many different things, some people have told me to just get a Suica card and then top it up whilst I am there, and that I don't have to book any train tickets (I can just hop on and go). Others have told me to get a JR Rail Pass as this would be more beneficial and means I can travel on any JR line as many times as I like within our 2 week stay.

Whilst we are in Akihabara, we are planning to Visit Osaka for one of the weekends we are there, we know we need to get the Shinkansen to do this (as it's faster) we would also be looking to visit Ueno park, Shinjuku, Tokyo and possibly Tokyo Disney Land. I assume to make the best of the JR Rail Pass, we would have to plan to travel quite a few times on the train.

SO! Can someone please tell me, in their own opinion, which would would benefit us more?
The Suica card (which we can top up, as and when)
The JR Rail Pass - Providing that we use the train enough times.

Thanks Everyone!
Donna