I don't know how early you'd have to get there.
It all depends. At least an hour or so before the doors open? So you can get in line..
I mean, if you're a huge fan then screw it and get GA tickets. Being in the crowd, to me, is way more fun. =)
And the reserved seats, I'm almost 100% will be numbered. Because there are assigned seats and rows.
In my opinion, GA are much much much better.
I've been to over a 150 concerts now, and they've mainly all been in the pit/on the floor.
If you want to get close, then you'd have to get there early and be ready to be 100% cramped with people.
If it's your first LP concert, and you're not sure of how you're going to react to being in a very large and close crowd, then it might be better to get reserved seats and have a nice relaxed view. :)