Aside from the similar name and a special photographic quirk they share, these two camera apps are very different.
Hipstamatic camera apps, both Disposable and the original model, are all about clever filters that "make digital photography look analog." Like Instagram, Hipstamatic images can be filtered and mutilated, especially if you pay extra for additional filters.
The new Disposable model adds a social feature, in which Facebook friends can share a "disposable camera," with 24 exposures overall. Only after the "roll" is shot can the people sharing the camera see all the photos and then share them, e-mail them, print them, etc.
It's just like those old disposables you used to see on tables at weddings. How clever.
But it is also a rather charming throwback to ye olde analog tymes, where taking care with your shots mattered, because you only had so much film, and it wasn't free. You didn't have gigabytes of wide-open storage to fill up at whim.
Hipstamatic Disposable pushes the metaphor by selling in-app camera packs (multiples of its 24-exposure "cameras") that have unique filter effects. At least the prices are not egregious: at the worst, a 9-pack of 24-exposure cameras costs 99 cents, or half a penny a shot. Enough to make you think, but it won't break you. (There are also unlimited-use camera filters available, again at 99 cents, on top of two no-charge disposable camera types that come with the free app.)
Dotti Disposable also works in camera-sized chunks. In this app's case, you buy 12-shot "rolls" for $4.99. What you get for that is the actual printing and physical delivery of your shots, as 4x6 photos sent through the mail, to the person you want. (Dotti works on Android as well as iOS.)
Sincerely's Dotti is selling an actual physical good so, appropriately, it's a bit less cutesy at the core: you can review all the images in a "roll" and delete the ones you don't like. Once all 12 shot slots are used up with good pictures, then you can send off a roll for processing.
Both apps are visually delightful. But I found Dotti both nicer looking and easier to use, thanks to a larger framing window and the post-photo deletion control. Dotti lacks the filters of Hipstamatic. I, for one, am fine with that.
I am generally not a fan of apps that ape old-fashioned or obsolete physical products in an attempt to be nostalgic. And these two apps do push the bounds of cuteness. But the idea of shooting in "rolls," especially rolls you're paying for, is not, actually, all that bad. It forces people to see a cost for each shutter click and to think about telling stories efficiently, in smaller numbers of images.
At least, that's what these "disposable" apps could do, in a pure and beautiful world. In reality, I think people will push back against these apps' constraints, and go quickly back to using unlimited apps and taking tons of pictures of everything, only sometimes doing the post-event edits to eliminate redundant or poor photographs.