Su Yu chose the Radiation Land as the battlefield, considering that he primarily uses Ghost Energy in combat now.
If he were to use his full power, even if he won, he'd leave behind a lot of radiation, which might affect the Mechanical City, requiring efforts to purify afterwards.
Might as well make the battlefield the Radiation Land directly, since it's already full of Ghost Energy Radiation, a little more wouldn't make a difference.
Moreover, Su Yu had long wanted to explore the Radiation Land to find materials that can withstand high-level Ghost Energy to craft the Brutal Battle Armor.
Now it's perfect to handle both matters together, and after defeating Tie Long, he could explore the Radiation Land incidentally.
Also, choosing his own battlefield could prevent any secret schemes from Tie Long.
"Radiation Land? Seems like he really has connections with the Ghost Empire..."
