Sneak Attack vs Cunning or Dream Thief

I need to get rid of Sneak Attack, every time my Meniss uses it instead of Shadow Swipe the ladder I get sad.

Im wondering, does Cunning's def lowering last forever or just that one turn and does Dream Thief ever get used at all? And would either be better than just using Shadow Swipe over and over until I enough MATK to 1 hit monsters until I die?

And do either of those moves proc instead of Shadow Swipe and is the raised attack power of those moves make enough of a difference to make Shadow Swipe redundant?

last for ever and decrease MDef again if used a 2nd and 3rd time.

Dream Thief is never used in ladder

Alright so is the self buff potential of Shadow Swipe better than taking the hit with for more upfront damage with Cunning? Assuming Im using hypno-jinx which could help me tank some hits and makes Dream Thief much more useful to me during PvP and regular levels.

teach ambush, if u haven't