One watches the sentence. One reads the book.
ProWritingAid is at its strongest in the line: grammar, style, readability, the repeated word, the over-long sentence. It catches the things a copy-editor catches, as you write, and it slots into the editor you already use.
DraftProse asks a different question. The Reader is not about whether a sentence is correct, it is about whether the book holds: where the pacing clusters, how the plot architecture sits, whether a character still sounds like themselves across the whole manuscript.