What's the difference?

[nobap]

What's the difference, if any, between
彼は医者になることを決心した。
彼は医者になる決心をした。
彼は医者になろうと決心した。
?

Are they interchangeable?

Thanks a lot.

[j_bertoni2279]

The first two are about the same, as far as I know. The last one isn't making sense to me yet, but it might be a grammar pattern I haven't learned.

[keimizutani19912666]

Hi, nobep.

There is no great difference between these three for me; I'm Japanese.

[brad12]

can you distinguish between manga and japanese anime?