RE: About disposable diapers -- what causes accidents...
Not sure where the accident is occurring-- out the sides, up the back, up the front (eww!)?
In general, our experience with these kinds of accidents were up the back, and were because we needed to move up a size because DS was too tall for the current size diaper. If you use a diaper with stretch, there's usually lots of room around the middle, so you may run out of room lengthwise first. We've always moved up in size before the weight on the package indicated it b/c DS is so tall. The exception is the last size change, which happened because DS can load a Size 4 diaper with urine faster than you can blink an eye, so we moved to Size 5.
If it's out the legs, it's probably the fit at the legs. We had to learn the hard way to make sure the leg gathers of the cuff of the diaper were always pulled out (not tucked in) or we had leaks of both kinds. Otherwise, see if you've got a tight fit at the legs, but be sure it's not causing red marks that are too tight.
I'm a Pampers gal myself, since I work for the company. We tend to stick with Cruisers unless we're testing out the other products, so I don't have a lot of personal experience comparing other brands like Huggies on things like fit.
Based on conversations here and with friends IRL, different manufacturers' diapers tend to fit different sized babies better. Sometimes it's worth it to try another brand (and I mean any or all of them, not just mine!) to see if the fit is better for your particular kid. Good luck!
*Edited to make sure I'm clear about my intentions in this post :)
Heather
Mommy to DS (9/03) and DD (5/08)