I believe the new Magic Your Way tickets have made things a bit more complicated in determining whether an Annual Pass makes sense. There are far more options, plus a steeper drop-off in price as you add days (for one type of MYW pass, for example, the difference between a 6-day and 7-day pass is only $3.00).
There are significant discounts on the Disney hotels for Annual Passholders, so that can be a factor too, if you're staying onsite (and especially if you're staying in a deluxe resort, and/or off-season).
As for the 7- or 10-day tickets . . . I don't know that I can really offer advice, but I personally bought 7-day expiry tickets for my upcoming 7-day stay. Strictly based on the math it would have been cheaper per-day to buy 10-day tickets, but then I also figured that I might end up coming back for another 7-day vacation, and then I'd need to buy 4-day MYW passes, and then I wasn't so sure that I would have saved money. So, I took the easy safe route and bought the 7-day. But reasonable people can certainly disagree about the right way to go on that.