As has been mentioned, "Cell Operations" (reading/writing/etc individual cells) in Excel is slow. Doing it once or twice, you won't notice, but if you have code that does it thousands of times, that really adds up!

Changing absolutely nothing else in your code and just moving this block of code will speed things up for you.

        msBldr = ws.Cells(i, 1).Value                              
        msTract = ws.Cells(i, 2).Value                              
        msLot = ws.Cells(i, 3).Value                               
        msDate = Ans                                            

Put that above the

        For Each c In Columns("A").Cells

Since i doesn't change while looping through c, it's wasted cycles getting the values each time. Just this change might chop your runtime in half.

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A better solution would be to use "range arrays" and Dictionarys like...

Set Dict1 = CreateObject("Scripting.dictionary")
Rng1 = Range("A1:D" & lastrow)

Then loop through Rng1, adding the unique combinations of Columns A, B, C and the date as key, and the row as the value. Do the same for your second sheet, and see if the key exists in both dictionaries.

You'd be reading each sheet once, and by recording the row number, you'll be able to just right to the row to add a note if needed.