I'll try to answer what I can from my experiences in LARPing over seas. I guess the main things that take effect as to how things are differnt is the legal systems. There you can play as hard as you want, you get hurt through stupidity it is, for the most part, you own fault. Here a person trips and they have the right to sue everyone and thier mothers. Also LARPs are more accepted oer there are are reconized as a recreational sport.
The players take LARP with a passion I hardly ever see here in the states. They get up early to work on garb weapons armor and the like several hours befire work. They think about it at work a LOT and then when they get home they do what neds to be done and then back to LARP things. Although none of them would ever admit it it is a large contest to them. Who can have the best armor, the coolest weapons, the latest trends in fantasy garb, the coolest special effect for thier group ect. Then there are the units that pool together to make sure they look the best.
On the field it is acting and role playing to the best of their abilities. And they really get into it. A lot of LARPers in America hardly act or role play, there they do not hols back at all. We are talking yelling, sceaming, jumping diving, the whole nine yards. When they get hit they fall to the ground and let out blood chilling screams. The first time I heard one I was at Conquest. The person besie me got hit with an arrow. He fell to the fround and let out the louded howl of pain I ever heard. As I was right beside him I almost jumped out of my skin. He was drug to the rear of the fighting line where 3 or 4 people playing medics went to heal him. They pulled out bandages and tied him up where he was hit. The added blood packs into them so it looked like he was eally bleding. Then they called for a magical healer.
A good number of them (I would say about 90% or so) use home made or store bought latex weapons. The other 10% have some damn good duct tape covered weapons. Now I should warn you that they do not pull thier punches. When you are hit you know it. This is partly wy they insist that the armor be real. Thier armor requirements are just the tough as the SCA, if not worse in other areas. But armor is optional. I thought I didn't need armor and I would depend on my speed and skill to defend myself. After 10 minutes and several hits to the chest (which left welts) I elected to wear armor.
Of course it is hard to know what is going on for some parts as there were about 6 different languages being yelled at any given time. They also have that different languages are different race langauges. These are the ones I know what they are
German is common (as the LARP was held in Germany it sort of makes sense)
English was drow (So I was playing a human who spoke only Drow and some common)
The main thing they have is the if you can do it so can your character rule. So if you have a bow and arrow and know how to use them, so does your character. If you have no bloody clue as to how to fight with two weapons neither does your character. If you can't see anything in the dark, neither can your character. This last part really takes part in the under dark.
The under dark is part of the game field where all the 'evil' creatures camp. It covers about 4 to 5 acers and has light proof tarps covering the whole area so there is no light in there, except for what you bring with you. the 'monsters' you fight in there are other player characters. And to them you are a raiding party
They allow latex weapons, bows and arrows, crossbows, siege weapons, magical items (and believe me they are COOL I have 'magical helm' that allows me to see in the dark. This is done with the night vision scopes in the helm)
Like I said they put a LOT into the game and to them it is a bog contest as to who is has the better toys, acting ability, unit ect.
As for the LARPs there, yes there is a small row of venders, but most of the players make their own items. Think of a LARP where there are 5 to 6 armies (earth, air, fire, water, magic, evil) each army has close to 2000 players. Then add in the 20 or so merc houses each with close to 100 players in them. Throw in close to 500 to 600 staff and cast members with over 200 different plots, not counting the inter character relation plots, and that is what a large event is like.
I hope this helps a bit.