Lets think of the economical advantages of the two.
Point 1: Optimus Prime has his energon to power him. Now I'm not up on transformers, but I'm guessing its not the cheapest stuff in the galaxy. Also, since he can turn into a semi.... have you seen diesel gas prices lately?
The Gundam thing runs off a nuclear reactor. Expensive initial buy, and though expensive, can be renewed.
Advantage: Gundam
Point 2: Optimus Prime is all for anti-car theft, anti-smoking, and has presumable ties with the Planeteers (as seen in the old commercials).
The Gundam is known for blowing the crap out of anything in its way.
Advantage: Optimus Prime
Point 3: Optimus Prime is made on some crazy planet off in space. Production costs are unknown, but he's been running for years.
The Gundam was made in Japan, and everyone knows that imports are cheaper faster and generally hated by those loyal to american companies.
Advantage: Tie
Point 4: Optimus Prime has no pilot and is therefore very ergonomically designed, causing no discomfort to anyone operating him, which is no one.
The Gundam has to be controlled by a pilot which, in most cases, requires time and money for training.
Advantage: Optimus Prime
RESULTS:
A WINNER IS OPTIMUS PRIME!!!!