I have the 8x and I've bought my daughter the Play for Christmas, I don't have any Xiaomi handsets to compare them to unfortunately, but can compare them to the Samsung S8.
In comparison to my work Samsung S8, I much prefer using the 8x to it in operation, it feels just as nimble and I prefer the screen size (note I don't play games on it), but by the same token it isn't so "trouser pocketable" as the S8, but is better for media and browsing the 'net. The Play in my limited testing seems faster in games and is every so slightly smaller, but the same in operation as the 8x.
Downsides are the camera isn't quite as good as my S8 on either handset and the sound quality in calls and media isn't as good through the speakers, this can be forgiven as they are much cheaper devices. Battery life on both is excellent.
Personally, I think they were bargains and the only reason for not going with a Redmii Note 5 in my own case was the lack of NFC.
Hope that helps.
