Both methods allow for the measurement of Total dietary fiber as High Molecular Weight Dietary Fiber (HMWDF).
In method 1 in the assay protocol HMWDF is measured as its separate components of Insoluble Dietary Fiber (IDF) and Soluble Dietary Fiber that Precipitates in ethanol (SDFP). This is AOAC method 991.43
In method 2 this separation does not occur and HMWDF is measured as a whole. This is AOAC method 985.29.
Method 1 will therefore give a bit more information if this is required.
Method 2 is less hands on - less crucibles/filtering needed.
Method 1 however only has one pH change due to the buffer used.
Whereas method 2 has 2 pH changes due to the different buffer used.
Differences are summarised in note 1 page 9 of the assay protocol: Total Dietary Fiber (K-TDFR) Assay Protocol and also in figures 1&2 page 11-12
Please see the following video links for these methods which may be helpful