That won't be the only failure scenario; if someone edits the cell using any method to get into that editing mode and doesn't change the data and presses Enter (or moves off the cell with the arrow keys) it will still trigger the change event.
You will have to do as you say and compare old value with new value.
There is Application.undo but I wouldn't try to use it, especially in cases where the user has changed more than one cell at once, for example by pasting multiple cells, or by editing multiple cells at once by entering data into multiple cells using Ctrl+Enter.
There is user training too: if the user goes into editing a cell and decides they don't, after all, want to change it, get them to Esc from the cell, not press Enter.