Traditionally a 'b' stands for bit, while a 'B' stands for Byte (8 bits).
Also traditionally, Bytes (kilobytes, megabytes, gigabytes) are used when it is about storage (RAM, FDD, HDD or other), whereas when they talk about bandwidth or 'speed' (notice I put the '') , they talk in bits (gigabits per second, etc).
So no, I don't think it should be Gb in the title. GB is fine, since it's talking about RAM.