My question relates to this rare situation.
1)
So which transaction is more secure
-when I use the option "replace-by-fee" or
-when I do not use the option "replace-by-fee"
Depends on context. When the transactions are unconfirmed, merchants are more inclined to accept those transactions without optin replace-by-fee enabled when they have no confirmations since it can easily be replaced. When they have one confirmations, both are pretty much equally safe.
If I understand you right your answer refers to the situation when the sender is different from the receiver. So in your scenario it is only a risk for the receiver.
But this is not the scenario in which I am interested.
My question is in the setting when the address of the sender and the address of the receiver belong to the same person and this person only will transfer his BTC from one address to another:
So my question of post #1 refers to this situation:
If I am right, there is a very very very small risk that during a transaction bitcoins can be stolen. Or that somebody lose bitcoins through a transaction. (I do not mean the situation if the user has chosen a wrong address)
My question relates to this rare situation.
1)
So which transaction is more secure
-when I use the option "replace-by-fee" or
-when I do not use the option "replace-by-fee"
Or isn't there any difference in relation of steeling or losing BTC's ?