If your looking to have more points for your current home resort, finding an add-on with the same UY makes life a little easier. We have a 50 point contract with a different UY than our other (400+) AKV points. So, once a year, I transfer those 50 points to the other contract and then we use those points first when making our reservations. It works out well, but I really wish I would not have purchased a different UY. I purchased those other 50 points during the pre-3/21/11 madness, and in hind-sight, it probably was not a great move.
Unfortunately, with the current system, those transferred points do not show up on the member website, so I have to keep a mental note that they are there. Some DIS'ers have spreadsheets to keep track of their different UY's, but I have done that since it is only 50 points.
If your goal is to have two home resorts and alternate years at your two different homes with banking and borrowing, then it probably does not matter as much. Also, if you have two different UY at two different resorts, you can always do split stays with the two different contracts every year.
I would like to add some BWV points to our current AKV ownership as some point, and I would take any UY, even if it is not the same as our current Dec UY. In fact, I would prefer June, Aug or Sept, since we would primarily use our BWV during F&W.
