If you want to know if you're host in MW3, check the loading screen:
If it says "Awaiting Challenge....." - You're host
If it says Awaiting Connection...." You're NOT host
"Awaiting Challenge" basically means you're waiting for the other players to connect to your "server" (console)
"Awaiting Connection" means that you're attempting to connect to the host
In terms of host advantage, I want to make this clear.
I support an even playing field but from playing MW3 i don't think the devs have properly tested or can possibly provide an even playing field.
Reason being at this time, not everyone can be placed on an even playing field
The host is the server. The host has control over the match. The host can end it on their own terms.
Now with giving a host a disadvantage, you're giving them more reason to dashboard or matches constantly interrupting with multiple host migrations.
I'd rather have 1 host have a slight advantage rather 6 or 9 (for GW) players have an advantage over the host.
I don't think players with less than adequate connections or a player joining a foreign lobby should be given a "boost."
It gives players with decent connections to avoid host or somewhat look for ways to downgrade their connection.
At the end of the day, the host is the player/server running the match for you.
Without a host, there is no match.