Samsung A 70 or Xiaomi 9t?

Can you say which is better for my lifestyle because they cost about the same amount

I'm watching youtube / Netflix

and sometimes gamble a bit on the phone

which one is better?

I have heard different opinions from Snapdragon 675 and 730 are they different? And is for YouTube and so the display of Samsung a 70 really better?

"Lifestyle" hmm…

Personally, I would, without knowing the models exactly, tend to Samsung (almost guess).
Xiaomi is a newly emerging brand that will take the place Huawei has always had. But so 100% mature there's nothing. The mobile phones still have a lot of bugs and are not yet optimized enough to be really reliable. You get a lot of megapixels with the camera that does not work, because the software is absolutely immature.
The Xiaomi of a friend is not addressed after a system update and had to be exchanged. Generally the cell phones hang up quite often, etc, etc.

If you want a reliable phone, then take Samsung.

Popup Selfie is more stylish than any (drop) notch. Price / performance is at Xiaomi Top.

As I said I'm not the "hello my loves" selfie guy I just want to watch anime and play a bit

I do not care about photos