The gap between Kid Gohan and Majin Vegeta is either negligible or non-existent in contrast to the gap between SSJ2 Goku and Majin Vegeta being obvious to ki sensing. That's the only thing we know for sure.Majin Vegeta didn't struggle relying on his memory because Gohan had lost considerable power. Maybe Kid Gohan and Majin Vegeta are quite close in power.
Gap A remains unknown. (Z Sword Gohan/Fat Buu-type gap)
Gap B is big enough for Trunks to instantly know one of them is stronger. (SSJ Goku/Frieza-type gap)
