What benefit do you deem most important when negotiating/reviewing an offer for a new job?

Hmmm... Before I realized I had to pick only one (it said benefits not benefit), my votes as 401k and healthcare. I have limited post Army experience, but my screening criteria were both. My current (first) post retirement job offered free healthcare, and a better retirement plan than any other job I was looking at. Hours, impact, and job satisfaction also were on the list. Time off too... but that is an added benefit.

While advancement within the company is important to me, there are members of my family who have serious medical conditions. Taking care of them is my first priority.

For me, good affordable healthcare benefits. while I go purchase third party, group policies often have the best rates and lowest cost shares.

Now in descending order:

Clearly defined opportunity for advancement within the company
401(k) Contributions
Education reimbursement programs
Vacation time/Paid time off

Unless you already have a masters this one is a big perk as a MBA from a tier one B school can run 80k +. This is a double win as it cost nothing out of pocket and you get to keep you education when you leave the organization.

As a retiree we have Tri-Care at this time but as I look at the news and I can see Tri-care going away and us having to fund via Affordable Healthcare Act which means several hundreds of dollars per month. All these above are important but I feel health care is the most important

Being self employed I have to look at this from a different angle. Here in Denmark I get health insurance(but pay through the nose in taxes), so that lightens the load a bit, but retirement I guess is my number 1 priority. I don't trust stock markets and with the ups and downs lately of the Euro and the dollar, I've been cashing in on gold and silver. I don't have all my eggs in one basket.

My next one is vacation. I don't get any paid vacations unless I plan for it, so each year I set a little aside for this as well.

Next I have to think of my profession. I need to attend courses and clinics to keep up with the advances in my field, so money needs to be set aside for this.

Then I got to plan for the unexpected, new roof, vehicle repairs, you all know the drill, so some gets set aside for this.

Sometimes I wish I was working for someone else and they could do all the paper work and planning, but then when I'm out daily on my job doing what I plan and enjoying myself, well it's worth it.

All the above. You definitely have to be discussing all of these during the interview and negotiation process. People leave jobs and take jobs for a variety of reasons. But once hired, it's funny how fast some of the lesser important priorities all of a sudden become a priority. I say you should address all of them and go in with your eyes open.

As for the "Clearly defined opportunity for advancement within the company" one, that's going to be challenging for a hiring manager. You've only spoken a couple times and most hiring managers will be reluctant to stick their neck out too far in making any advancement commitments at the hiring stage of the game. They are well aware that the use of the word "opportunity" gets turned into "it will happen" by prospective employees.

its a tie between health care and the 401(k).

Healthcare, than 401k. Have negotiated two jobs since retirement, Healthcare packages come in a wide variety. Don't forget your dental and eyes!.

Dental!

So crucial.