How to determine suitability and efficiency of GPU mining

[ggbtctalk000]

I am looking at several factors, memory size, FP32/64. Which one is important?
I compared specs for several AMD and NVIDIA GPUs, it is rumored that AMD's GPUs are speicially suited for Cryptomining, but why?
It appears answer is in FP64 speed. (double floating point). Does mining software extensively use these calculations a lot?
Because in general AMD GPU's ratio of FP64 to FP32 is double the nvidia's.
Lot of AMD GPU's, for example, VEGA56,64 has  FP64/32 ratio of 16 whereas likes of 1080/2080 Nvidia is 32.
Select AMD GPU's MI lines i.e. MI50//MI60/MI100 has ratio of whopping 2 only meaning its FP64 ratio is monstrious.

[DannyHamilton]

GPU is not suitable for mining Bitcoin.  If you intend to mine Bitcoin, you need ASIC.

IF you are asking about altcoins, then this is the wrong place to ask.  Try the altcoin subforum.