Fastest Find Last Used Row in Worksheet

I have a spreadsheet with 5000 rows of data from column A to column E. To add a new entry, I need to find the last used row. Which is faster of the two below:
i=1
do while Activesheet.Range("A1").offset(i,0)<>vbnullstring
i=i+1
loop
OR

i=Activesheet.Cells(ActiveSheet.Rows.Count, "A").End(xlUp).Row

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The ActiveSheet.rows.Count returns over 1m rows. I find it hard to believe that this is faster than using a loop to check for a blank cell within in 5000 rows. Maybe the following is faster:

I=Activesheet.Cells(6000,"A").End(xlup).Row

Takes only column A

This one for entire sheet

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Cheers
Leo