The laptop uses the S2 sleep mode by default instead of S3, which leads to draining a lot of battery during sleep.
Though this is intentional by the manufacturer and might cause lockups when forced I - @moredread - never had any issues with it.
See https://wiki.archlinux.org/index.php/Dell_XPS_13_(9370)#Power_Management and https://bugzilla.kernel.org/show_bug.cgi?id=199689#c3 for reference
- Arch linux wiki: Dell XPS 13 9370