Now where is the Lumia 640 XS when you need it... I'd much rather have a 4" phone than a 5" one. The previous 4.5" one was already pushing it for me.
I used to feel this way too but as I became acclimated to a ~4.5" device I now find it's merely adequate. I find myself headed for a 5" device next upgrade.
Anyway the specs seem decent and the phones look like nice mid-range models. The article should mention that the smaller one definitely has an LED flash like it's sibling, even if it doesn't get the better (and larger) camera/lens combo. Also the 640 says the battery is removable, I assume that applies to the XL as well? Both come with larger stock batteries than I would have expected out of mid-range Lumias. These models of SoCs/displays don't generally eat up as much power as high-end models so battery life should be good. Even so, being user-replaceable is great and opens the door for upgraded capacities for those who crave it.
As for the keyboard I really like that it works with all the popular devices. Also, very neat that it can connect to two devices at once and switch between them with the tap of a button.