The question is so totally unspecific that it cannot be answered at all.
In a 8-Rescue Deck? I'd go for Hax anytime.
Otherwise? Then Rescue seems to be at a loss anyway.
And generally, I still think that leaders are in most cases not as helpful as another card that fits into the group(s) played.
Ambre is a leader and she can give anyone in your deck a courage: Power+3. While Hax only gives himself the courage: Power+3 just like DerMagus said it depends on the situation. Are you using a Rescue deck or you just want someone with that ability or something?