Eric, in my experiment, the Clayton fixer cleared and fixed about 30% slower than TF4 and about the same as the Kodak fix. It was claimed that it fixed about 30% FASTER. That is not so.
The extent of fixation is identical in all cases. It has to remove all silver halide.
The wash rate with TF4 is about 2 - 4 x faster than with the Kodak and Clayton fixers.
Therefore overall, the TF-4 is more effective. As I mentioned above, it is possible to do even better.