Get a pair of Unions!!! Burton bindings are shit and they will end up breaking on you. Unions will last you longer than any other. Don't waste your money on any other binding. I have said this before and I will say it agian... I swear by Union.
I second the Unions. Been thrashing mine for their 3rd season, about 60-80 days a year, and nothing has gone wrong on them. I'd say by the end of the year I'll replace the toe straps because of rail abuse but that's still only $15 for replacements. The best part is they haven't changed the design for 4 years now. Same solid stuff year after year.
I have heard nothing but good about Union Datas, 390's or cartels. Although flow is a great company i've heard more bad then good about them, but it seems that everybody that has them loves them and I heard as soon as you get them adjusted properly to your liking they're golden. Good Luck!
i would take a look into the ride rx bindings however if your looking for a flexy binding they may not be for you. I just think that they have good build quality with aluminum instead of plastic on most of the binding. I got some nice 07-08 RXs on a spring sale for like $99. They also have a convertable toe strap so you can wear it over the toes of over the top. I personally like over the toes, it seems to take away from the pressure that over the top generates on your foot since the boot is stiffer at the toe region.