Having played a lot of online tournaments mostly freerolls
it must be said, your friend has it right
If you want to finish off well you need the chips, sure it can be done without them but then you need the cards.
Having finished second out of 200 2 weeks ago I was chip leader with about 40ish to go. When you build up a bigger stack and you are getting down to the business end of the tournament, you will find a lot of people will tighten up.
This is due to them not wanting to get knocked out and usually sneak into the money. Now this is the time to start making moves and stealing pots and raising.
The advantage you will have when you have more chips is that people won't won't to play against you cause you have enough chips to knock them out. You can also afford to raise the blinds a lot more often, specially the shorter stacks out there. This also can have the benefit of them trying to protect their blinds and make a move with their short stack in order to double up and stay in. If they do this they will usually have weaker cards than they like and you can often bust them out. This means less players so closer to the prize and also more chips for you ;]
The other side to it is they want to last as long as possible so just hand the chips over. The one thing to bear in mind is though not to tussle with the other large stacks without a premium hand. You can still be crippled rather easily, don't be afraid to let pots go if you have plenty of chips. At this point its easy to steal some blinds and antes to get them back if you are patient.
The larger stack will also allow you to sit out and fold a few rounds letting other people battle it out. Pick your moments. Having a shorter stack means the blinds and antes will always be nabbing at you and the larger stacks will try to bully you. If your getting low on chips don't leave it too late to start making moves. If you do then you will find yourself just folding to try and outlast other low stacks, you might sneak in the money but its the 1st 2nd and 3rd spots that usually have the largest percentage of the prize pool.