We joined
DVC in October (bought AKV), and I booked our first stay at the 7-month mark for a BCV studio the first week of June. I was worried about getting a BCV reservation, especially for summer, but it worked out.
I'm guessing a ressie for 3 studios might be a little tougher, but maybe if you are flexible with dates or the villa size, you could improve your chances.
You don't mention wanting to stay at BLT, but if that interests you at all, then I would think that it would also be a benefit to owning there...it seems that BLT (particularly MK view villas) may be a tough reservation to get for awhile. Also, if you ever want the option of booking a Grand Villa, BCV does not have these, while BLT does (along with AKV, BWV, OKW, and SSR).
The prevailing opinion here seems to be "Buy where you want to stay." I agree with that philosophy, with perhaps a bit of a modification: "Buy where you want to stay, or at least buy where you won't mind staying and where it will give you the best deal/value for your purchase situation."
Personally, I want to stay at the Poly, but unfortunately, there isn't a DVC option there.

So, my next choice was the only DVC on the monorail - BLT. But when we looked at the cost, incentives, etc., we decided AKV was the better value. We've stayed at AK Lodge before and had an enjoyable stay there, and if that is the only place we are ever able to get a ressie, we are OK with that (and even happier if we are lucky enough to get Concierge!

).
All you are really guaranteed with your DVC purchase is a stay at your home resort...if you could only use your points to stay at BLT, would you be happy there? If the answer is "yes," then you can feel comfortable buying there and trying for BCV (or another resort) at 7 months. If the answer is "no," then you should probably buy BCV, even if it means losing out on incentives and the extra years on the contract.
Sorry if this is more info than you wanted...hope it helps!