most likely the .60 will be easier to fly for a couple of reasons that i can think of...

with a bigger engine you won't need as much of a runway that the .46 would need ...

bigger planes are usually more stable to fly and easier to see in the air

having more speed will make doing some stunts easier but since it's a trainer you're going to be limited

i doubt you will really notice a huge difference from either size trainer, i personally would save the money and buy the.46 size
but it's up to you