…resting/slain in the Spirit and ecstasy?
I could be wrong but I don’t think one loses consciousness or falls down during ecstasy.
It seems to me that the usual setting for ‘slain in the Spirit’ is in Charismatic prayer events.
It can involve a healing or a grace, but doesn’t signify that the person already had a deep prayer life.
Ecstasy tends to relate to a deeper spiritual life of prayer especially within the state of prayer called Contemplation, and is sometimes associated with particular saints like St Teresa of Avila/Jesus. That is my understanding of the difference.
I don’t know, but I know that seeing someone “slain in the spirit” as a kid gave me nightmares for a long time afterword.