The DC33 has a larger bin, but overall i think the DC25 would be best, the handle/wand is metal and rigid unlike the DC33.
The head is also smaller on the DC25 so you can get the head of the cleaner under low furniture. And the DC25 has stiffer bristles on the brushbar.
The DC25 all floor/anmial are the exact same machine! The only difference is colour, and with the animal you get a turbine attachment for pet hair (for sofa's, chair, stairs etc.)
Or if you could wait till nect year dyson should be releasing a new ball!
And remember whichever dyson you buy empty and clean filters thoroughly, regulary!