Toddler bike seat vs. bike trailer?
I've had both. A really nice trailer and a child bike seat -- where the child sits between the rider and the handlebar (like this WeeRide Kangaroo Child Bike Seat).



My daughter was ok with the trailer, but absolutely preferred the seat.

I found with the seat in front of me, the weight didn't affect me almost at all, and if the bike was going to fall, I'd be in a much better position to protect my child (since she's directly in front of me).

We used that for a long time and never ever had an issue (and let's face it, with the kid along for the ride, you're not likely to ever ride like a madman, right?)

She's six years old, and still misses it (we stopped when she was about 3.5 yrs old--just getting too big!)