Yes, toys are harder to house train, not because of brains, because of physical limitations. My aunt had a toy and a mini, and several of my friends had toys, HOWEVER, it's still much MUCH easier than other small breeds. They just have tiny systems, tiny bladders and all, and it makes things harder on them physically.
Also, being in an apartment, barking is a serious consideration. Toys are usually yappers and toy females are more vocal than males. Not saying there aren't toy females that are quiet, but I've yet to see it. Several on this forum with toys also have stated, they sure do yip a lot compared to their mini's or standards.
If you want very small, you can get a small 10 pound miniature. They can be as short as 10 or 11 inches (they can be much larger as well.) If your heart is set on a toy (they sure are very very precious) make sure you work with it at an early age on barking.
Male vs Female
Males are more affectionate (as a rule, though I knew a Standard lady that loved me to the point of me wanting to steal her :sinister: ) and more lazy. They bark less as well and don't get the mood swings females do.
Just trying to cover all bases, so you make sure you get a buddy that suits your lifestyle and living accommodations.
Fantastic write up (book PDF) on poodles