I’ve only tried GTX cards… but if the ATI’s are cheaper for similar hashing power then I would use those.
I haven’t overclocked my GTX because I want it to last – I use it for VR and gaming.
I started mining last night and have received around 50 $music in 12 hours with one GTX card hashing at 20 Mh/s.
I’ve used a 1060, 1070 and 1080 - and I would recommend 1060s - you can get 2 for the price of a 1070 and mine much faster.
1060s hash around 20 Mh/s - cost around $250 new
1070s hash around 25 Mh/s - cost around $400 new
1080s hash around 20 Mh/s - cost around $500 new
1080s are very slow at hashing due to memory type !!
hope that helps!