Mediatek has no secure element afaik. Or if they have, it is way less secure than a pixels. This means the phone will have very little brute force protection and weaker encryption.
The OS will not be hardened in any way.
Also, it is proprietary as hell. GrapheneOS is completely, entirely, open source. Even the configs for every server they run is.
Dont trust random marketing garbage if nobody can look at the code.
If your code is public and everyone looks at it, it has to be good. Proprietary software can, and often is, very badly written because nobody externally looks at it.
This also includes some audits. I guess there are good audits, good companies or whoever does these, but many are just "look at the code for a day, run 10 test suites, thats it.
So please, I hope you never honestly consider buying a proprietary phone, and see it as in any way comparable. It cant be.