In the end it is truly about personal prefernce.
Jesus taught us how to pray to God, "Our Father..." these were his instructions and as such, shoudl take precedent over anythign else, UNLESS one does NOT recognise the authority of Jesus.
In a far more "personal view", the degree of personal relationship we have with God through Jesus tends to dictate how comfortable we are with certain terms.
JW have no personal relationship with Jesus and God hence the choice of the term "jehovah".
Anyone can call me Paul (My name) and when I hear Father I think "formal", but when my little ones call me "daddy" my heart melts.
I can't help but think that it works the same way with our beloved heavenly father.