You might find it helpful to look at this direct comparison of hardware specs between those two models:
https://www.gsmarena.com/compare.php3?idPhone1=9521&idPhone2=9507
Look through the various aspects and see if one stands out as the better choice to match what you want. The Mi 9 does have a more robust CPU and GPU but it's not a matter where the Note 7 is lacking in system resource capacity. Just compare each feature one at a time and list which are important to you -- the Mi 9 has slightly more cellular frequency support, something that might be an advantage if you switch carriers (emphasize 'might') and an AMOLED display, but the Note 7 has a higher capacity battery, a consideration if you plan on using your phone a lot between charges and an IPS LED display; the Mi9 has better cameras (main and selfie) and a front fingerprint sensor but the Note 7 has a head phone jack and a rear fingerprint sensor; etc.