One question I’ve never worked out is, with a sudoku that you’d find in a newspaper, will you ever have a situation where you have to try a number and see if it leads to a contradiction (as opposed to using logic to determine which number to put in). I have never come across a problem that I know for sure I needed to guess a number, and if I did I probably wouldn’t want to try it. Hence, I didn’t want to use a recursive method, and I accept it means that there are some sudokus that I won’t be able to solve.

So it then comes down to, how you want to balance the trade-off between the steps being intuitive and it being guaranteed to always solve puzzles.