Yes well generally AMD video cards are hotter. Not just when mining, but while gaming as well as while idle. More recent cards have better cooling though and the temperature also depends on your room, ambient temperature, how clean the fan is, etc. Check the best OC settings for your card to ensure you are not wasting electricity. It's known that while mining cards can hit 80°C, high end Nvidia cards operate safely at 100 as well, though for gaming (not persistently).