hi, im also new here, but i think i can help you with this. Check out this link, https://litecoin.info/Mining_hardware_comparison. XFX 7970 should be doing 710kH/s, provided your setting is correct. The information in the link is just an estimation or sample kH/s people provided but it does give us a pretty good idea regarding the hashrate of the cards. Regarding which card is better to get, it varies from people to people. 7970 draws more current than 7950 but it has higher hashrate. You can do more research regarding the details of these cards.