Smoking/grillings steaks - cast iron versus aluminum

For the purposes of searing steaks, would you recommend the cast iron griddle or the grillgrate set? I'm thinking the cast iron will reduce moisture loss?
https://www.atbbq.com/accessories/bbq-a ... iddle.html
https://www.atbbq.com/accessories/bbq-a ... grill.html
Thanks in advance!
https://www.atbbq.com/accessories/bbq-a ... iddle.html
https://www.atbbq.com/accessories/bbq-a ... grill.html
Thanks in advance!