The first one is the original letter, which is a valid letter that can be used as non-italic, bold, capitalized, as part of words, etc.
The second one is specific to represent the Planck's Constant. It is the same h with stroke
, but it's only italic small letter, not valid part of words.
So, if you're writing Maltese words, use U+0127. If you're writing physics equations, use U+210f.