Go with the trailer. For one thing, you’re getting very close to the load limit of most child bike seats—40 pounds. For another, I don’t like the idea of having a bike that top-heavy on any sort of trail. Also, there’s a better chance of your child’s head snapping around. If they’re sitting low to the ground, they’ll be much more stable.

I concede that a bike seat is the cheaper option. Most, such as the Topeak Babysitter (topeak.com), are around $125. A good trailer, such as the Burley Solo (burley.com), runs $350. But the Burley supports more weight than a seat (75 pounds), offers more seating options for your child, has more protection for the passenger than a bike seat (roll cage construction), and can carry both the yougster and a range of other stuff you might decide you need. On trails, a dual-wheel trailer can pose challenges because the wheels are wider than your bike. If you’re on well maintained trails it shouldn’t be an issue, but you’ll want to keep that in mind.

The usual safety rules still apply: helmet for you and for the child (Bell’s Trigger works well, $30; bellhelmets.com), and make sure the helmet is snug and level. It drives me nuts when I see kids pedaling along or in a trailer or on a bike seat with the helmet canted way back so their forehead is exposed. Most impacts are in the frontal area of the skull, so the helmet must come down over the forehead.

You’ve seen our picks for 2007 Gear of the Year, and now the entire Outside Summer Buyer’s Guide is online. Check out this year’s more than 400 must-have gear items, including tents.