Hello! I was with the same questions, I decided to go for the A52 LTE (5g version is still not available in Argentina but it's almost the same) , the three of them are great options, i would stick to Redmi and Samsung, this is my order:

Samsung -- Redmi -- Poco

basically because of this points:

- Availability: in my country (Argentina) Samsung is far more popular here and cheaper than Xiaomi or Poco, i bought it in 6 interest-free fees at my phone carrier. For POCO & Redmi phones you have to buy it from resellers/importers and in a non-official store.

- Company support: Samsung said that the A52 is going to have support for 3-4 years at least, so it's a good thing to have if planning to use your cell for a quite long time. Redmi/POCO has good support, but they hav ea different business model, it seems that they don't care so much in mantaining long term updates but making new phones constantly. The good thing is that it's easier to install a custom ROM in them.

-Bloatware: The three of them has bloatware, but i think samsun is the cleanest of the three in this aspect (not talking about flashing a custom ROM in POCO/REDMI, but they are mantained by random developers, so same as point #2, you are not 100% sure of receiving updates).

- Dust protection: A52 is the only of the three that has certified dust/water protection

- Headphones: This is a weak aspect for A52, it doesnt have proper components for the Jack, so you can have poor sound quality when using it.

- Finger Unlock: I personally prefer side unlock instead of screen unlock.

- Design: I dont like POCO design, and between Samsung/Redmi i like RM a little bit more, but the samsung matte plastic is nice also, so happy still.-Camera: Good on the 3, check youtube comparisons for this, also there are gcam version available if u want to experiment.

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As a side note, if Redmi were more available here than Samsung, i would get it probably, it looks like a great device

Hope it helps!