I actually have the same dilemma, in Holland the prices for 5600xt and 5700 overlap quite a bit. So the choice is get one of the very cheapest 5700's or a reputable well reviewed 5600xt.
In my case the choice between Sapphire 5600xt pulse or Asrock Challenger 5700.
Both 320 euro.
The Asrock runs kinda hot, and makes a bit more noise.
Noise is a personal choice I guess
Temperature...so it runs a bit hotter than others, should i really care much ?
Any other arguments to go for a high end 5600xt over a cheap 5700?