Among those that can and can not, not any difference. But there are in the same group in Group Manger.
Permissions of default group:
g:bukkit_default:
permissions:
- bukkit.broadcast.user
- -bukkit.command.plugins
- sg.arena.join
- sg.arena.vote
- sg.lobby.join
- kitpvp.kit.pvp
- kitpvp.kit.archer
- essentials.warp
- votekick.start
- votekick.kick
- paintball.general
- essentials.kit
- BattleKits.use.archer
- BattleKits.use.heavy
- BattleKits.bypassRestriction.disable-player-drops-on-death
- BattleKits.bypassRestriction.disable-hunger
- BattleKits.bypassRestriction.disable-player-drops-on-death
- BattleKits.bypassRestriction.disable-crafting
- BattleKits.bypassRestriction.disable-player-xp-drop
- BattleKits.bypassRestriction.disable-mob-xp-drop
- BattleKits.bypassRestriction.disable-block-xp
- BattleKits.bypassRestriction.disable-inventory-interaction
- BattleKits.bypassRestriction.disable-pickup-items
- BattleKits.bypassRestriction.disable-block-break
- BattleKits.bypassRestriction.disable-block-place
- BattleKits.bypassRestriction.hide-death-messages
- BattleKits.bypassRestriction.disable-inventory-click
- buttoncommands.use.normal

My config:

Global BattleKits settings

Add world-specific blocks by warapping everything in the name of the world.

Restrictions are handled by permissions now.

settings:
once-per-life: false
auto-update: false
enable-restrictions: true
show-kit-info-on-respawn: false
override-disable-respawn-kits: false
instant-soup-drink: false
instant-soup-drink:
replenish-type: hunger
signs:
ignore-permissions: false
ignore-costs: false
ignore-world-restriction: false
ignore-lives-restriction: false
indirect:
ignore-costs: false
ignore-permissions: false
ignore-world-restriction: false
ignore-lives-restriction: false
rewards:
killCommands:

• xp 1L

My kits:

http://pastebin.com/Z8qxtNuW

Anyone who has the permissions BattleKits.bypassRestriction.disable-dropping-items will be able to drop them. I'd suggest negating that permission by puttin a dash in front of it.

They don't have this permission.

I'll look into it, but so far tests have shown that there are no issues with the restriction system.
https://docs.google.com/a/infinitenight.net/spreadsheet/ccc?key=0Ai8_JDvk_gAjdHppTThrMFZ4RmdhVTBzZUR3a3QtMEE

What version are you using?