I play both with my 8 year old. I would say he really likes both, probably Survive a little more. Personally, I like Forbidden Desert more, but really both of them are good
. I think your biggest thing to decide is what will be better received a cooperative game or a competitive game? That is really the kicker in the question.
A little competition is always good - we play Hanabi co-operatively, and that works ok, because we can always moan at each other for making the wrong choice. However, we loathed Flashpoint because it was so co-operative heavy - so I guess competitive will likely win.