This is from a professional musician standpoint. I personally feel like when u first learn a song, it should be in the original key because that is the key chosen by the artist. Once learned, then u can play it in any key you want. You can disagree if u want, it's all good.
I agree.
I (also) find that since I don't have perfect pitch, I can use a number of recorded songs to help me discover a key someone is singing in.
It's also easier (most of the time) for me to start a song in the key I heard it being sung in on the original recording (that's not to say I can sing it all in that key, but it sound's weird i,n the start, if it's not in the original key).
my 1 cent.
ps:
My sis likes to take sing most songs in Db or Bb, so if I think of her starting certain songs, I know for sure I am singing in Bb or Db.
But hey cats, do it anyhow you want..I like to know the original key & then all the other keys.