Either would work well for you. But given the choice, I'd pick March or September because you may have to walk a studio reservation for the October time frame. You cannot successfully walk across use years.
You will love the Poly. Having 3 people in those studios sounds pretty dreamy.Alright, so I think it will be Poly. Expensive resort, but it speaks to me.Well not more/much more expensive to buy than CCV, but more per night. Or, MAYBE 50/50 Poly CCV, but seems like ”a lot of work”, combining and such.
I showed videos of the resort for my family, and they preferred poly to CCV.
I know, I’m buying it ”unseen”, but i have researched for 15 months.
now I just need to find my unicorn contract.
It does cost more points though, as you know, so I would strongly recommend getting all 100 points there. I do enjoy doing split stays when we plan it that way, but I don’t like being forced into split-stays bc of lack of points. 
We loooove the Skyliner! My boys’ favorite resort is a toss-up btw Beach Club (the pool & Skyliner access) and Riviera (the rooms & Skyliner attached)... are you seeing a theme?I think the studios will work fine for us for several years, because we are a family of three. My daughter will love the bed that folds out from the wall. Then I will add-on at riviera or boardwalk for my favorite ride at WDW: the Skyliner.
If I mostly travel in oct-nov or possibly march-april in the future for longer easter break: Will it be best with oct use year or march?
Just my opinion, but I wouldn’t choose the Boardwalk for actually using Skyliner bc you walk away from HS- to Epcot- just to fly back to HS. Even at BC, I couldn’t bear getting to HS via Skyliner (it takes longer than just walking, for sure!)... but I did let them Skyline back to BC for our afternoon breaks at Stormalong Bay & again in the evenings. It was wonderful!! 
It seems that the BW would work well for your goal to economize, and as long as you’re happy to just ride the Skyliner & not utilizing it to cut down on travel time, I’m sure you’d love it there ).
The banking deadline for August use years is the following March 31. With an August use year, your May vacations could be an issue if you have to cancel it after the preceding March 31. (April vacations are OK because if you cancel it after the preceding March 31, the points would go into holding and couldn't be banked anyway). Same logic applies to September use years.
Ideally, your UY would be just before when you typically travel. So since you would normally be going in Nov-Dec or March-May, an October UY would be ideal. The four non-bankable months for an October contract is June-Sept and none of those months fall into your travel months. By having an October UY you could most likely cancel any of your reservations and still be OK to bank those points if you needed to (depending on when you cancel, of course). Remember, UY primarily matters if you think you will be cancelling reservations. We were looking for October when we bought, but we ended up getting a June UY because the deal was too good to pass up. April break is a time of year when we can make WDW trips work, but April falls into our 4 month window of not being able to bank. We don't plan on cancelling any reservations, so we just went with the really good June UY deal we found. But I would hold out and keep looking for an October UY if you can...it would offer better peace of mind.
