We are a family of 4 with a just turned 2 year old and a 5 year old. We bought DVC bc specifically we like staying in one bedrooms with our young kids for 4 reasons:
1) Separate sleeping spaces for napping/early to bed kids
2) Full kitchen (we feed our kids a lot in the villa bc they just don't eat enough to justify buying them meals in the parks)
3) In-unit washer dryer (I never did laundry on any vacation ever until I had kids, but I find this so helpful with little ones)
4) Extra square footage bc we tend to spend more time in the villa taking breaks now that we have kids
We feel like (and we could be very wrong about this) when our kids are older we won't need the one bedroom anymore and can start staying in studios again. We figure that while separate sleeping spaces might always be nice, once our kids are a few years older, they won't be napping, so we won't NEED the separate space during the day, and we also won't neeeeed the full kitchen and washer dryer as much as we do now. My family of 4 always traveled together in one hotel room...but we didn't really start traveling until my sister and I were 7 and 4, whereas we started traveling with my own children from the time each was about three months old. Also once our kids are much older and involved in activities, there will always be the possibility of one parent taking one kid at a time, or something like that. But right now, when we are always all traveling together, and bringing the occasional grandparent or aunt/uncle, and with a lot more baggage, both literally and figuratively, the one bedrooms are ideal for families with small kids.