The Quad core CPU has twice the performance of the Dual core CPU.
An Intel Dual core i5/i7 CPU will geekbench score about 6800
An Intel Quad core i5 or i7 CPU will geekbench score over 12000
Your best value macbook pro is the base model 15-inch with Quad core CPU and 16gb ram
128gb SSD is more than enough for most people if you are just going to use the basic app with iwork.
265gb SSD is better
512gb SSD if you plan on using boot camp and dual boot OSX / MS-Windows
1tb SSD if you plan on storing allot of files like music and videos.
I recommend a Quad core CPU as my 2012 MBP with dual core i5 CPU is beginning to show its age and lose it performance.
I have a 512gb SSD with boot camp installed Dual boot OSX Sierra / MS Windows-10 loaded with many , many, many apps. Just about all of them and I am only using about half the SSD Space.
I don't have any music or videos however.
If I want to store Music or Videos I would use a USB flash drive that way I will never lose my files if the MBP should fail.
https://www.amazon.com/Samsung-128GB-Flash-MUF-128BB-AM/dp/B017DH3O5A/ref=sr_1_8 ?s=pc&ie=UTF8&qid=1498669445&sr=1-8&keywords=usb+flash+drive