CME GGM Growth vs Equity VAL GGM Growth - Real vs Nominal

Alright…can someone help me here. For GGM, should we use real growth or nominal.

Reading 16 Equity:

Cobb Douglas given real, and states that real is better for GGM since it less us compare countries, etc.

Reading 15 CME:

Growth rate in nominal terms. Earnings growth rate = GDP Growth Rate + Excess corporate growth.

Should we only use real when given using Cobb to solve? Thanks!