This is a tough question because you have to compare circumstances...
Some questions to consider:
How old are you versus how old are your children? Starting a savings plan for high school aged children might not give you the best benefit. Starting a savings plan (assuming you opt for a 529 plan) for younger children allows you to accrue more tax free or tax deferred growth.
How old are you? Do you have other savings or retirement plans? Can you count on Social Security?
Does your employer offers a matching plan for retirement contributions? If so, it might make sense to participate because you're doubling your savings.
Does your state offers a 529 plan that allows you to buy college credits at today's prices? If so, and your children are small, you may be able to offset the spiraling costs of college today.
Also consider that contributions to most retirement plans results in a tax deduction today for federal purposes while saving with a 529 plan does not (though there may be some state tax savings depending on your state).
That probably didn't give you an answer but I hope it gives you some food for thought. I recommend that you sit down with a financial planner and run some numbers - that way, you can look at your specific situation and see what works best for you.

Money is fungible (it's green no matter what you spend it on), so the general principle is to pursue a strategy that maximizes your overall return on investment. If that means investing in a college savings plan, you'll then need to spend less from current income to pay for college, freeing up money for retirement. And vice versa.

This yields a free key principles:

(1) Maximize the match. If your employer matches retirement plan contributions up to a limit, save to that limit. It's free money. Likewise, if your state allows you to deduct contributions to your college savings plan from your state income tax return, contribute up to that limit.

(2) Rank all savings vehicles and debt according to the after tax interest rate or return on investment, and direct any extra money to the highest rate. Paying off debt, after all, is like getting a tax-free return on investment equal to the interest rate. This can get tricky. For example, mortgage interest is deductible, but it only adds value to the extent that itemization is greater than the standard deduction. Student loan interest (for qualified education loans) is also deductible, but only up to $2,500 a year. However, that is an above-the-line deduction (technically, an exclusion from income), meaning that you can use it even if you stick with the standard deduction.

I discuss this in greater detail at FinAid in the section that discusses prioritizing savings.