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NEW YORK (CNN/Money) - I'm unsure how much I should contribute to my 401(k). One expert says you should contribute the max, even if it's beyond what the company matches. Another says to limit the contribution to the amount the company will max, and then direct the rest of your money to prepaying your mortgage.

The theory there is that tax rates are very low today and thus could rise in the future, which means by fully funding your 401(k), you'd be avoiding low tax bill today for a higher one tomorrow. What do you think is the right course?

-- Shoma, Waukesha, Wisconsin

When it comes to saving and investing for retirement, I think the best course for most people is to keep things as simple as possible. When things get complicated, people can get caught up in the details of investment strategies and lose sight of what's really most important: accumulating a retirement nest egg that can carry you through a retirement that can easily last 30 or more years.

Given that outlook, I think it's a perfectly acceptable strategy for most people to contribute the maximum to their 401(k). Yes, it's possible that higher tax rates rise in the future could put you into a higher tax bracket and thus erode the tax-benefit of a 401(k).

But if that were to happen -- and, remember, we don't know what tax rates will be in the future -- it's not as if your 401(k) balance would become worthless. You would still benefit from the tax-free compounding of gains before you withdraw your money. It just wouldn't be as sweet a deal as it would be if tax rates remain the same or fall.

I also think there are practical reasons that simply sticking to a 401(k) makes sense, the biggest being that it's so convenient. Once you sign up, you don't have to do anything. The money is automatically deducted from your paycheck and goes into your 401(k).

The biggest problem most people face in building a retirement nest egg isn't finding the best investing strategy to make their money grow. It's saving the money in the first place. The fact that 401(k)s make this so easy is a huge plus in their favor -- and a reason why I consider fully funding a 401(k) a good idea even if it doesn't turn out to be (with the benefit of hindsight) the absolute best strategy.

That said, I do think there is a good way to hedge against the possibility of higher tax rates in the future. Instead of fully funding your 401(k), you contribute just enough to get your employer's match. You then take the money you would have contributed beyond the match and use it to open up a Roth IRA.

This year, you can contribute up to $4,000 in a Roth, plus another $500 in "catch-up" contributions if you're 50 or older. If you still have money left to save after fully funding the Roth, then funnel that money back into your 401(k).

You don't get a tax-deduction for the money you put into the Roth. But you pay no income tax on any of your Roth money when you withdraw it at retirement. (For Roth eligibility requirements and other details about these accounts, click here.) If tax rates go up after you've retired, the money you pull out of the Roth account wouldn't be hurt by the higher rates.

Starting next year, you may even be able to pull off this strategy without opening a Roth. How? Well, starting in 2006, employers have the option of offering Roth 401(k) accounts, basically 401(k)s that you fund with after-tax dollars. As with a Roth, you don't get a tax break for the contribution, but withdrawals are tax-free. More than 30 percent of employers surveyed by employee benefit consulting firm Hewitt Associates said they intend to offer the 401(k).

This little strategy of combining a traditional 401(k) with a Roth IRA (or Roth 401(k)) provides what I like to call "tax diversification." Essentially, it allows you to hedge your bets about future tax rates. If you end up in a higher tax bracket in retirement, then the Roth is the better deal from a tax standpoint. If you end up in a lower tax bracket, then your 401(k) stash is the better deal. If you're in the same tax bracket, it's a wash.

Having two pots of money that are taxed in different ways also gives you more flexibility in terms of managing your withdrawals during retirement to yield the biggest after-tax payment. And a Roth also has several advantages beyond its tax treatment. For more on the various benefits tax diversification can offer, I suggest you check out an earlier story I wrote on this concept.

But I can't stress enough that you should only embark on this strategy if you're sure you'll carry it out. If you limit your 401(k) contribution and then never get around to opening that Roth IRA, you'll be sabotaging your retirement security.

As for foregoing 401(k) contributions to prepay your mortgage, I'm not saying it's a lousy strategy, but it's not one I'd recommend -- at least not initially. By prepaying your mortgage, your "return" is essentially the after-tax cost of the mortgage interest you avoid paying. I think you should be able to earn at least that much with a diversified investment portfolio these days.

If you're closing in on retirement and you've already accumulated a nice fat nest egg, then you may want to consider shaving down your mortgage balance so you don't have it hanging over you in retirement. But during your career, I believe the focus of your retirement plan should be investing as much as you can in tax-advantaged accounts like 401(k)s, IRAs and Roth IRAs that will give you easy access to the cash you'll need for living expenses once you retire.

Walter Updegrave is a senior editor at MONEY Magazine and is the author of "We're Not in Kansas Anymore: Strategies for Retiring Rich in a Totally Changed World."