Sliced cheese is almost the laziest form of making cheese on toast (obviously ripping cheese flavoured plastic slices off other cheese flavoured plastic slices is the laziest (and most vile) ).
The slice issue is riddled with problems:
1. The cheese tends to be too thick, and needs extra melting, which often causes "Burnt Edge" syndrome.
2. L&P issue noted above.
3. No left over grated cheese! The biggest advantage to grating cheese, is grating too much and then grabbing handfuls of one of the best snacks ever. I don't know what chemical transformation cheese goes through when it's grated, but it goes from great to sublime!
4. You lose the adventurous surface of a grated cheese on toast landscape. Your pallet climbing the mountains, and tongue down the troughs of grated cheesiness is an oral fantasy come true... Or something. Grated cheese on toast is rolling Alton Towers, to a sliced, flat Flamingoland!
Where are the Welsh members anyway in this topic??? Come on, this is your national dish! You've got to have some say in the matter!
Oh, and for those of you struggling with grated fingers, I've provided a quick reference to grating: