Roland Of Gilead :
No, you don't need to use DDU. Both GPU's are in the same driver revision. Just to a 'clean' install of the latest driver and you're good to go.
Agree with mjbn1977, it can't hurt
Most instructional videos on how to use DDU on an GPU upgrade is rather vague,
How i see it would go like this (Please correct me if im wrong)
1. Download geforce experiance installer and DDU installer
2. Open DDU in safe mode and select option that clears drivers and shutsdown the pc, it says in brackets for GPU upgrades.
3. Once pc is shutdown physically install the 1070 and start up pc
4. PC should start wiith horrific resolution due to there being no drivers, i would then re-install geforce experiance and perform a clean install of drivers from that
5. Finally reboot once more to make sure of proper install
Is that right or is there a better way?