Same goal, different strengths / weaknesses.

GitHub has really focussed on preventing credential leaks. It's particularly good at scanning for highly identifiable patterns and preventing pushes that include them. That makes sense for GitHub: they're in the best position to prevent leaks (by rolling out push protection to all users) and they're big enough to influence the industry to switch to using highly identifiable patterns for API keys. However, it's at the expense of scanning for unstructured secrets (like passwords) where GitHub isn't as deep yet.

TruffleHog has focussed on scanning for credentials _after_ they've leaked. They scan for a broader range of things (including unstructured secrets like passwords). That naturally has a higher false positive rate, which they combat by automatically verifying some of their findings (by making requests to the corresponding services). GitHub does that too (for patterns it can't push protect) but it hasn't gone as deep on it yet. The delta is relatively small, though - as you can imagine, it's a long tail of patterns / credential types.

Right now there's space for both solutions - you want prevention when you can get it (without creating a bad developer experience with false positives), but you also want breadth. In the long run, though, GitHub is probably better positioned to offer both.