I've been looking to get a new mattress, for around ¥100,000~200,000.
After some research, the most fitting ones I found are the Nitori N-Sleep luxury 3 normal (soft) and the Koala Supreme.
I tested them both in the showrooms and they felt equally comfortable, just the sweet spot between soft and firm.

But they are very different (pocket coil vs foam), and I am not sure how they will feel over time, so I wanted to know if you guys had some experience with either of these mattresses.

To summarize;

• The Nitori model might be cooler in summer thanks to the more breathable pocket coil design, hold my back better and sag less with my weight (~85kg). But I am afraid the top pad will get bad/flat faster and I'll start feeling the coils, as it's what some users mentioned. I hate feeling the coils in mattresses.
• The Koala supreme model allows to flip the middle pad to make it harder or softer, and the top pad to make it cooler or warmer, which is very nice. But I'm doubtful about the efficiency of that cooling pad (the Nitori "N-Cool" bed covers never did much for me), I'm also afraid it's going to become too soft after a few years and stop holding my back well.
• Koala allows 120 days trial and Nitori doesn't, so good point for Koala there, but I'm not sure how complicated it is to send it back.