PSNR vs SSIM_Structural similarity technique

[LeoKac]

please, tell me which Structural similarity technique is better by quality, PSNR or SSIM?

[Selur]

Structural similarity technique is better by quality,

define quality, if your definition of quality can not be described by a formula both will probably only give vague hints.
for most people SSIM better meats the perceived quality than PSNR, especially if the data rates are not so high,..
normally a good value in heuristic X can as easily fail as a good value in heuristic Y
-> there are tons of comparisons and papers about video/image quality metrics and there is no absolute winner