Like the title implies, which is your favorite? In case you aren't familiar with the Super Robot Taisen terminology, I've given a brief description of the two below.
Real Robots: These robots utilize technology that is common-place in their universe. Some examples of this are most of the Gundam series, Macross, etc.
Super Robots: These bad boys use unique technology, often alien or supernatural in nature. Some examples of this are GaoGaiGar, Getter Robo, Mazinger Z, any of the Yuusha robot shows, etc.