Honestly the difference between each of them is close to insignificant, as well as between those 3 and any other Linux Distro.
Sure BT5 has a kernel BoF protection that is slightly better than Ubuntu, then again, you can probably just tweak your Ubuntu and have it too, maybe it's just some configuration file with some safe-mode:off.
Bottom line I think the best Distro to have is the one that fits you better. I like the optimization of Slackware, but it has some problems when it comes to recognize external devices in terminal, first you have to check GUI, then it updates the /media/ list (maybe there's a command to update device list, but honestly I kind aquit after that)
The other thing that you can take in consideration is the number of existent applications for each distro and the ones that are portable to other distros. (BT5 and Ubuntu applications are usually(if not all) portable).
With all that said I can tell you I've had some distros:
Ubuntu
Slackware
Arch Linux
Debian
BT5
nUbuntu
Maybe some more?
You have to try them yourself.