I'm using xubuntu 18.04 on a Thinkpad. Previously I used xubuntu 14.04 and 16.04. On 14.04 resume after suspend would get to a password prompt immediately. 16.04 was noticeably slower. 18.04 is worse. It takes several seconds with the disk activity light flashing away. Once I get logged back in it seems that WiFi isn't available for 15+ seconds and often has to be restarted.
I installed Arch Linux with XFCE on a USB drive on the same laptop and resuming from suspend is instantaneous. And no WiFi restart issues.
So what's going on with resume? Is it the display manager or systemd or XFCE that handles suspend/resume? Where should I be looking to trouble shoot this? For security and battery life I just want to close the lid on my laptop without worrying about resume hassles. I could switch to Arch Linux for my laptop but I prefer xubuntu.