Can't help much, but think you are wise to investigate thoroughly before giving in to the temptation to purchase a different use year contract.
To me, the biggest issue / concern is online booking. Sometimes, you just need to book right at 8 am Eastern when you are using the 7 month window (or even the 11 month window).
AFAIK, there aren't online booking problems if you intend to use the contracts separately. For example, use contract one to stay at resort A in the spring and contract two to stay at resort B in the fall.
I do believe you will have online booking issues if you need to use points from both contracts for the same reservation. MS can handle, but I do not think the online system can. Others in this situation will have real experiences to offer.
FWIW, given all the tech issues with the
DVC system, I would personally avoid any & all complexity if I had a choice. I have one master contract with an add-on (for same resort) and have NEVER had any of the issues that others frequently describe here with any of the Disney systems, including
MDE, DVC Member site, booking engine, ticket purchases and ADRs. Perhaps I am lucky, but IMO, the simple straightforward cases are the easiest for the programmers to get right and the first to get stabilized if something does go wrong.
Good luck!