请教-- to handle this situation

interviewed at company A Wednesday, got offer Friday. The agent told me before it was a 3 or 1 months contract leading to full time. A gave me an offer of full time. But a few things I don't like,
1. salary very low - A is a smaller company, and the position they offer relatively intermediate level.
2. location, commute will 1-1.5 hour.
technical environment seems not bad.

At the same, another agent send me an openning at company B too, it was quiet a few days, then Friday I was called for an interview next week. I asked the agent if can be arranged earlier, she asked do you have offer now, I said yes. she said she will talk to the hiring manager of company B. today, she told me the manager is away this week, so the interview will be next week, I said okay.
I like company B more, cause,
1. salary will be much better.
2. location is very convenient for me.
3. company B is very big.

Today I have to send back the offer letter from company A. and I was surposed to start there this week too. right now, I am not working, cut off from my previous company. given current economy, I want to play safe.

Any suggestion on handling the offer and the interview? thanks a lot!