I own both games and they are both great! Tethered got me fully addicted and i played it through to the end within a couple of days. Maybe i spent 10-15 hours total on the game (finishing the campaign and then playing a bit more).
It is totally cute, immersive, challenging and fun. But since there is no multiplayer mode i have not returned to the game after finishing it.
In death i've maybe spent 4 hours in so far (got it 2 weeks ago). Its really immersive and cool. The design of the game makes me think it has alot of replayability since the world is randomly generated each time you play and there are alot of unlocks and enemies as you progress. Its a bit brutal and even scary as the adrenaline flows when enemies jump at you. After i play about an hour and then die i find it to hard to play anymore that same day (after you die you have to start over from the beginning). I will make a new attempt this weekend for sure.
Tethered is all about strategy (rts), multitasking skills, and cuteness. In death is all about having balls of steel and steady hands because if you miss a few arrows you might get your face chewed off by a horde of zombies.
However, one of the main reasons I bought it was so that I could have a more "relaxed" type of gaming experience. But as you progress through the game, it gets harder and requires more quick RTS -style thinking and reaction. Granted, this is not a bad thing, but it goes against what I was hoping to get out of this particular game.
I would prefer for Tethered to be more of a slow-paced SIM as opposed to a true RTS. But the game really does offer quite a bit of fun and challenge in a rather addictive way.