>>9733371That's a really hard question. Something I've learned from collecting plushies is that there's so many different types of softness but they all feel good in different ways. These two in Pic related can both be described as minky but there are differences between them that are very hard to put into words.
I'd say a good thing to look out for is a minky smooth texture. At the same time, I know some people are really into fluffy or furry plushies. Aside from texture, I'd say the most important thing is getting plushies that are stuffed well. This ensures that they will be enjoyable to hug for a long time.