Bustin' Out gives you a more active role, as your Sim, instead of just commanding them.
The Sims Bustin' Out for the GBA is more of an adventure game than an actual sim. Sure, you have to take care of your character by sleeping, feeding etc. But most of the game is about completing objectives, most of the time by collecting some things, doing certain activities or talking to a specific person. And while doing this you'll unlock new territories, and the jobs, public places, houses and people there.
It still has some sim aspects. You can't create your own house, but you cán buy one, and buy furniture to put in it. Though unlike the pc-versions of the game, here you have a limit to the ammount of stuff in your house. You can simply recoulor all of your furniture with one press of a button, so you can give your house an entire new look without having to spend any money.
Making money is done by mini-games that are opened at certain times of the day. They're easy to play, and there's a set score which you'll need to get to the next level of the game, which means that you get to earn more money next time. Every mini-game has five levels to it. They involve mowing the lawn, fishing, lifting weights, diving off a cliff, and more.
Creating your Sim is pretty simple. You get to choose a haircut and it's colour, your skin colour, and the colours of your shirt, pants/skirt, and shoes. You do get to give points to create a personality though. It won't really affect the game, so it's kinda worthless. It's nice that it's there, but what good is it if it doesn't do anything?
Communicating is done nicely. You'll start off by getting a simple greeting from the person you're talking to, and then you get three sentences, and it's up to you to choose what your Sim is going to say next, which will lead to a reply of the other Sim, and give you yet another three sentences.
All in all, it's a nice variation to the Sims, suitable to kill the time when you're not in range of an actual pc to play it's big brother.