Many fixed-income investors were thrilled last fall by the chance to buy inflation-indexed U.S. Savings bonds paying nearly 6 percent. They had to hurry, as new rates were to be set Nov. 1. Sure enough, the rate since then has been 4.4 percent.

But 4.4 percent seems OK compared to the 2 percent and 3 percent paid these days by short-term bank-savings and money-market accounts.

So should investors rush to grab the current batch of I Bonds before the new  probably lower  rates are announced May 1?

Probably not, says Daniel J. Pederson, author of “Savings Bonds: When to Hold, When to Fold and Everything In-Between.” These days, he says, investors will probably do better with Patriot Bonds  old-fashioned EE bonds, renamed after Sept. 11.

The reason has to do with the two-part yield paid by I Bonds  a fixed rate good for the 30-year life of the bond, and a floating rate designed to go up or down every six months to match the inflation rate.

When combined, the two rates assure that the bond will always beat inflation by an amount equal to the fixed rate.

Six months ago, I Bonds were appealing because the fixed rate was 3 percent and the floating rate 2.92 percent, guaranteeing a “real” yield  that is, after inflation  of 3 percent for 30 years.

But on Nov. 1, the fixed rate for new bonds fell to 2 percent and the floating rate was reset to 2.4 percent, for a combined 4.4 percent.

The combined rate for the next batch of bonds, issued after April 30, is likely to go down further, since the floating rate will drop to reflect falling inflation, Pederson says.

At first glance, that makes today’s I Bonds look more attractive than the ones to come. But Pederson says that if the inflation rate falls to zero, the floating rate on today’s bonds would fall to zero, causing the combined rate to drop to just 2 percent.

Since few people would want bonds paying so little, Pederson thinks the government may raise  not lower  the fixed rate above today’s 2 percent on new bonds. So people who want I Bonds are probably better off focusing on the fixed rate  and waiting for the new bonds, he says.

But he argues that investors will probably do even better with Patriot Bonds. Those sold through the end of April will pay 4.07 percent for the first six months after purchase. Then the rate will adjust every six months.

Rates on old and new Patriot Bonds are reset every six months to 90 percent of the average paid by five-year Treasury notes over the previous six months. The Treasury rate is governed by supply and demand, and rates have been rising as investors bet that the economy will rebound. Currently, the five-year Treasury yields nearly 4.8 percent, up from about 3.5 percent in November. Pederson expects Patriots to pay 3.5 percent to 4 percent after May 1. Anyone who purchases before then will get the current 4.07 percent for six months.

Pederson says Patriots are the better choice whenever the fixed rate on I Bonds is below 2.6 percent.

Why not get the five-year Treasury and earn a tad more? That’s fine if you can afford to. The cheapest Treasury costs $1,000, while savings bonds go for as little as $25 each.

Anyone buying Treasuries also should plan on keeping them until they mature. At that point, you’re sure of receiving the full principal, or face value of the bond  $1,000 for a $1,000 bond, for instance. But if you want to sell the bond early, you could receive less if prevailing rates have gone up in the meantime, since investors would rather have newer bonds yielding more.

With savings bonds, you don’t face this “interest-rate risk.”

Your principal is always safe and never declines. Savings bonds can be redeemed as early as six months after they are purchased, though you lose the latest three months of interest earnings if you redeem before five years.

If you want Patriots, go ahead and buy them now. If you insist on I Bonds, it’s probably better to wait until May 1.

Many banks sell savings bonds, and you also can get them online at www.savingsbonds.gov.