-reindex:

• wipes the chainstate (the UTXO set)
• wipes the block index (the database with information about which block is where on disk)
• rebuilds the block index (by going over all blk*.dat files, and finding things in it that look like blocks)
• rebuilds the chainstate (redoing all validation for blocks) based on the blocks now in the index

-reindex-chainstate:

• wipes the chainstate
• rebuilds the chainstate using the blocks in the index you had before

The latter should be strictly faster, as it does not need to rebuild the block index first. Perhaps the progress bar during reindex confuses you: that progress is only for the rebuilding of the index. The recreation of the chainstate happens after that rebuild is completed.

You should use -reindex only when you were running in pruning mode, or if you suspect the blocks on disk are actually corrupted. Otherwise, when you only suspect corruption of the chainstate (which is far more likely), use -reindex-chainstate.