The answer is they don't fit well together. `perf-tools` is probably the most complete tool when it comes to number of performance counters, which be aggregated

The answer is they don't fit well together. `perf-tools` is probably the most complete tool when it comes to number of performance counters, which be aggregated. However it is not well composable or extensible - so you have to use it as it is. I also find the code hard to read. `bcc` and `lttng` try to make things by creating a more usable API. They partially reuse the kernel part of `perf` (aka `perf_events`) and also add their own kernel modules to provide new functionality.