Clarifications on the difficulty

[piricullo]

Hello,
I'm relatively new to mining, for now I'm mining with an nVidia GT1030 video card (which I already had) and a specifically purchased RX580.
The thing that is not clear to me is how the difficulty works.
Let me explain better, for now I am mining ETN, with ccminer and with the GT1030 I have about 135 H / s, with the RX580 and xmr-stak instead about 800 H / s.
The thing that is unclear is that at the number of hashrates accepted by the RX580 are not at all 6 times those of the GT1030, but almost double.
I have already checked with HWInfo that there are no errors, so the only parameter that changes is the difficulty that the pool assigns to the worker.
What does it mean? That difficulty decreases me the number of accepted hashrates? And if so, in theory it is better to have more economic cards (which consume even less) rather than a very fast one?

Thanks and bye

[MagicSmoker]

Many pools set the difficulty for each share (portion of a block) based on your hashrate so your faster card is getting more difficult (ie, larger/more valuable) shares to mine.

[piricullo]

Ok,
very helpful.

Thank you