Do not let a downswing get you down (as long as you were sticking to your strategy and not letting emotion or tilt splash your money away.
If you are playing "correctly" and getting beaten by 27o via a preflop shove busting big slick or cowboys, well, that's just probability. It's going to happen. And sometimes it is going to happen all at once, hand after hand.
The things which should make you consider switching games is when you follow a strat, and you lose, not because of luck, but by being beaten by better play. Either you need to adjust or you need to get out in such circumstances. (I'm still trying to adjust!).
From another perspective, I think cash games tend to be much tighter affairs. You're not fighting against time in the same way as with the merciless advancement of the blinds. With MTT's it is about staying ahead so you can reach the final table. With cash games, you've already made the final table just by sitting down.
With cash, it is about how much money can you make per hour. With MTT's, you're trying to make it to the cashes.
I suggest you play the game which gives you the most reward. This may be monetary, or it may simply be the pleasure of the game. Keep working and keep moving forward!
Cheers,
ObbleeXY