401k and 403b plans are actually the same thing - 401k plans are for for-profit companies, and 403b plans are for non-profit companies, schools, government agencies, etc.

The same funds and stocks are available to both 401k and 403b plans, it just depends on who the manager of your fund is, and which funds he has selected. You can have your HR department contact the fund manager and ask him to provide a wider range of funds to choose from, or you can open your own retirement account (an IRA, which functions very much the same as a 401k or 403b, except its a personal account) at any bank or financial broker. Usually companies have access to better deals/funds than individuals can access, so it's better to go through your company plan.

Frankly, any of your coworkers who are NOT accepting the 403b and are missing out on the company's matching contributions are being extremely foolish. Would you pass up a $100 bill sitting on the sidewalk? That's what they are doing by not opening this account - the company is offering free money and they aren't taking it! They are also being reckless with their future by not investing in any sort of retirement account - IRAs and 403bs offer great tax advantages: it reduces your amount of taxable income, so you pay less in taxes each year, and the investment grows tax-free!

Your coworkers probably don't really understand what 401k are and how they work. You might to suggest some of the following books to them - they are very easy to understand and explain how small investments now can turn you into a millionaire upon retirement.
-The Complete Idiot's Guide to Managing Your Money
-The Automatic Millionaire, by David Bach

Ok, for starters, saying no to free money is just plain dumb.

403(b) plans are typically reserved for employees of public schools and tax-exempt organizations and are amazingly similar to 401(k) plans in that they allow participants to make a salary deferral contributions into a tax-sheltered retirement account.

Perhaps your associates are simply unhappy with their investment elections, but are you really going to listen to people that are telling their employer they don't want that 6% FREE extra money?

From your standpoint, there is very little difference between a 403(b) and a 401(k). Both are before-tax retirement accounts which can hold mutual funds and which you contribute money to. When you leave your job, either one can be rolled over to your next employer's plan or a Rollover IRA.

The main difference is from the company's side. 401(k)'s are for profit organizations, while 403(b)'s are for non-profit organizations.

Unfortunately, many 403(b)s are run with high-cost variable annuities. This might be the reason that your coworkers are complaining.