Thank you in advance
Never sat in the front for Billy Elliot so I can't compare but I always sit in the front row for Jersey Boys.
I've sat in all three tiers of the theatre but I feel much more involved sitting right at the front, it's like being at a personal concert. The first time you go and sit down you think you're going to see nothing because the stage is pretty high but I'm only 5 ft 2 and I don't find it a problem. I took my friend for her birthday the other week and it was the first time she'd been and she loved the seats.
If the cast are in the middle of the stage I can't see from mid-calves up but for the majority of the main musical performances they're much nearer the edge of the stage or moving about so you can see all the dances and everything. There are 2 or 3 scenes where I lose sight of 1 or 2 of the characters for 30 seconds or so but it doesn't affect the story and just hearing the lines is enough.
Hope this helps a bit