Hi Fred,
Both can be interesting. In case of the one with the boxes it is an extra region-sudoku, which means less givens are necessary, thus can be interesting. On the other hand also without the boxes can be interesting, but there must be more givens in the grid.

Recently I made two of these puzzles for the puzzle-portal of Logic Masters Germany.
The first one (7x7) turned out to be confusing. You can find it here:

http://www.logic-masters.de/Raetselportal/Raetsel/zeigen.php?id=000...

Some solvers suggested the use of colours, what I did in the second one (8x8).
You can find it here:

http://www.logic-masters.de/Raetselportal/Raetsel/zeigen.php?id=000...

But I still don't know if I like it better with colors. In my opinion the lines are not necessary now, because of the colours.
Anyway, today the last one will appear. It's a 9x9 grid to finish the small series.

Best regards,
Richard