My wife and I are 72 and 77 years old and must cash or roll over 401K and 403B accounts that were employer managed and now being cancelled with current Financial Management Co. What is the difference between the 401K and the 403B accounts? What would be our best choice of a roll over investment? We are considering Certificate of Deposits with an insured source with highest yield. Is an IRA an option for best income tax ?

There isn't much difference. The benefits of the two types of plans are the same. The main difference is that 401ks have more requirements (i.e. an outside auditor) and, as such, have been designated for for-profit companies, which presumably and theoretically are better able to handle the cost of compliance. 501(c)3 not-for-profits and self-employed individuals were given a break by Congress (lucky them... ); they get to use 403bs, which offer the benefits of 401ks without some of the hassles in terms of compliance.

You could reinvest some of your 401k/403b proceeds in a Roth IRA. Here are the qualification criteria:
Basic Rules for Regular Contributions. Since Roths grow completely tax free, this is your best reinvestment option. But you can only contribute $5,000 per individual per year.

CDs are certainly "safe." Personally, I think the rates right now are terrible though and, instead, would look at a money market until rates come back up. ETrade is paying 3 percent on its basic savings account which is FDIC insured. That's a full point and a half better than CDs right now. USA Today publishes the nation's best CD and money market payment rates once a week, I believe.

You might consider interviewing a few certified financial planners to help you with this. Make sure you get someone who charges by the hour and not someone who charges a percentage of your total assets or a commission each time they buy for you (see Edward Jones). This way you know your financial advisor does not have any conflicts of interest.

Good luck.