As far as square footage, OKW has the largest Villas on property. there will be more room for the Pack and Play for your 1 y/o at OKW.
We stayed in a 1BR at OKW for the first time last year over labor day weekend and we were SHOCKED at how much larger the rooms are.
We have stayed at SSR, AKV, BLT, VWL, and BCV and OKW's rooms are by far the largest.
As far as the pools - Saratoga Springs has the new Paddock Pool opening up this summer - and the High Rock Springs Pool is a little more kid friendly than AKW.
The choice is tough - but at the end of the day when everyone needs some space to themselves - and a place to unwind - OKW is going to give you more square footage.
However OKW does not have a counter service restaurant with indoor seating - it has a couple counter service places near the pools - but not a dedicated place to sit down out of the sun, the heat, and potentially rain.
Saratoga Springs has a great counter service restaurant - but the walk from various parts of the resort can be long and hot.
At either resort you are either a walk or a boat ride away from Downtown Disney!
One last consideration is the bus transportation - SSR has had some pretty horrific bus wait times at different times of the year. On the other hand, there isn't a 'best' place to stay at OKW in terms of busing. If you stay in the Hospitality House area you have to ride the entire resort loop to get to your bus stop which is the last one.
If you are driving, you won't have a problem!
It's a tough call - but at the end of the day, you have to look at how much time you will be spending in the room, at the resort, by the pool, etc etc to determine which one fits your needs the best.
We loved OKW - and we loved SSR.