Hi! I didn't know about it until I started with amigrumis, I was more into crocheting clothes and carpet as ( sorry forgot the word on English). For me it's easier the X when I'm making realistic dolls ( easier to grab the yard). When I want to make the amigurumi a little bit bigger with the same materials ( hook and yarn) I use the V shape but I have notices that if Im going to embroider the eyes the V makes it harder to do it. Im really don't know if that's the case or it's just me who really don't enjoy so much working with needles. :)
I prefer the "x" look for dolls because it looks neater like you said. It does make the fabric tighter, so for other things like blankets and towels I use the yarn over method. I don't do much crochet though and always learning!
I prefer the X with amigurumi. It does make the item smaller for me so that might be something to pay attention to if you're making something a particular size.