Differences between dmesg and journalctl -k for hardware failure monitoring

If I want to set up hardware failure monitoring which is better? Will either of these sources capture all relevant hardware failure, or are there other sources as well?

Currently I have a service looking at journalctl -k for messages with priority <= 3, but can be configured, I assume 4 is too noisy though, it then classifies logs based on common patterns, if unmatched will just be unclassified but you can still see the message. Sends the log to Elastic where it can then be alerted upon.