It's been reported as a bug that they don't show you the information, but, they basically have double and triple the capacity of the base one.
Though, I'm not entirely sure the better ones do transfer the heat faster, they just have a capacity. when you think about how pipes work, the bigger pipes are actually slower, so while the higher tier heatpipes do have a higher capacity and flow rate, the fact that they do have a higher capacity means they take longer to heat up, but I guess when things are up and running, they'll run for longer.