Is a higher joule rating always better?

Not strictly. Joules indicate how much surge energy the MOVs inside can absorb before failing, so higher is generally better for longevity, but specialist electrical communities point out that clamping voltage and response time matter as much. A 4,000-joule strip with a high clamping voltage may protect less effectively than a lower-joule unit with tighter clamping. Look for UL 1449 listing and ideally an auto-shutoff once protection is spent.