In 1984 what are Winston's advantages and disadvantages of being an outsider when he starts to rebel against the party?

Technically speaking, Winston is an insider, at least to
the extent that many people in his society are.  He isn't one of the proles, and works
in the Ministry of Truth.  So, he is technically part of the infrastructure of the
government, which makes him an insider of sorts.  He has started to rebel, in his mind
and heart, long before the novel even starts.  Even from the opening pages, we see that
Winston is unhappy, questioning of the government and the way that life is, and
searching for someone like-minded to connect with. At his apartment, he has been writing
down his persona, and rather rebellious thoughts for quite some time in a journal of
sorts, out of view of the cameras.  So, his rebellion began long before we meet him at
the beginning of the novel.

His first overt act of
rebellion, however, comes in his relationship with Julia.  Before this point, he has
only looked and people and wondered about their status, and whether they feel the same. 
He never has the courage to act on it.  Julia, when she initiates, gives Winston hope
that someone else is out there who feels like he does.  Going to meet her is his first
act of open rebellion.  Before that, he had done little things like buy the journal,
visited the prole section of the city, etc.  But meeting Julia is huge, and potentially
life-threatening if discovered.

As a person who works
inside of the Ministry of Truth, Winston has a distinct advantage in knowing,
first-hand, that his government lies and changes history in order to maintain its
power.  He knows this, and that information works to his advantage in the fact that it
is something that he has over the government, but it is to his disadvantage because it
irks him, and makes him unhappy and discontented to know that is being controlled by a
bunch of liars.  So, it works both ways for him.  Because he does work where he does, it
is a disadvantage because he is more closely watched.  The proles, for example, are
mostly left alone, but Winston, because he is privy to the government's secrets, is
watched like a hawk for any signs of rebellion or treachery. That is a huge
disadvantage, and one that keeps him from being happy.

He
is an outsider to the inner circle of the Party, and that is a disadvantage because he
does not get the nice things, does not have the privileges that those members do, and
does not have the truth behind their plans or the power to gain his freedom and
happiness.  It is a disadvantage becuase he never knows that he is being watched, and so
acts in ways that leads to his torture.  Being an outsider to the inner party is an
advantage in the fact that he does not know their darker secrets and so can't be held
accountable for them.

I hope all of those thought helped;
good luck!