I'm a traffic engineer in N. MI, been doing it for 11 years. Here are a few things I'd recommend... A couple are probably reiterated from previous posters.
1) Money is great, but it's not everything. You gotta decide what you want out of a job and what makes you happy in general. If you value your free time and have hobbies to pursue, it's not worth being in a job that makes you miserable for an extra $10k a year -IMO, at least.
2) Ask them what the company work culture is. How many hours a week do they typically see someone in your position working? Does that tend to fluctuate throughout the year? (Keep a poker face when they give you an answer -be ready for any number) If you'll be on salary (i.e. no 1.5 OT pay), then 60+ hours a week for $70k is way different than 40 hours a week for $70k.
3) Before accepting any offer, ask for a tour of the office and to meet your potential coworkers. Read their body language! Do they look haggard, like they're getting worked to death? Are they cheerful and enjoy being there? Is there already a company softball/bowling/hockey team where people make a point to hang out with each other even when not at work? That's usually a good sign.
4) Benefits package is important and should absolutely be considered as part of the total compensation! According to our HR website, mine's a little less than 40% of my total compensation.
5) Do they have a percentage of your salary that they'll automatically put into a 401k for you? Do they do a 401k match above & beyond that?
6) Ask them if there's room for growth/promotion from this position, and what that timeline and path might look like. (I started at $40k, but two years later it was closer to $60k) Ask about future training opportunities. It shows that you are eager and want to learn.
7)A large corporation will have different pros & cons than a small 15 person company will have -depends on what you're looking for.
8) Ask them any other questions that show that you're looking to help that company make money. And listen to what they have to say. Remember that that's what they're looking for, and if they feel you'll bring them profit, then they'll invest in you.
Good luck with all of it! GR is a great area with a lot of good stuff going on. Off topic, but if you like a good burger, try the Broadway Bar. Corner of 6th & Broadway, NW.