Aluminum or Plastic fuel cell?

I am very close to being ready to install my drivetrain in the Dart.
The cell will be around 15G and car will be a mostly weekend driven as it is too far to work everyday.
Was wondering on the selction between Aluminum and Plastic when it comes to buying.
I like the idea of Aluminum because of the strength and durability, but like the idea of the Plastic because of the cheap fuel and what it may do to the Aluminum tank on the inside.
All opinons are welcome,
Thanks,