LPIC certification: "Vendor neutral," meaning you need to memorize (note I said memorize, not learn) how both Debian and RHEL do things. For example, you'll be tested both on YUM and APT.

LPIC certifications are multiple choice, and really come down to rote memorization of flags. You're also tested on stuff of questionable relevance, like X11, desktop environments, and CUPS. If you're supporting Linux desktops, that stuff is probably important. But Linux deployed mostly on servers.

RHSA: RHEL/CentOS-only, and performance based. You can use man pages during the exam, so you can concentrate what commands do what and how to configure things. This is opposed to LPIC, where you're more focused on obscure flags.

Ubuntu has no vendor-specific exam. If you really want to stick with Debian/Ubuntu, go with the Linux Foundation certs. They're performance-based and you can choose to do it on Debian.