Well, the legs and ears are a really long story but basically (even in the videos and pictures) they have been mildly defective since he arrived. One of the legs has a very slight bend (maybe a cm or so) and it causes him to fall down a lot more on his left side (same side the ear motor is broken - but not the ear itself) even when he's running on stable software. For instance, on DogsLife, he falls down every 10-15 minutes (and not the rollover "trick"). And the ear motor itself actually works but a part of it is broken so that the ear constantly pops off. The only replacement for this is to replace the ear motor. Because the limb release lever for the head was already damaged (and I didn't want to potentially do more damage by fishing for it through McGyver tactics, wolfbob is going to send me the part and already sent me a description on how to take it apart and replace it - it doesn't look too complicated). There isn't anything you should be on the lookout for, Crewella has the full (undiplomatic) story haha. I've just kept it out of the public forums.
I used a paper clip per wolfbob's instructions and, after some trouble (mostly me being too cautious) everything came off easily with no damage to the release levers. Essentially I unwound a paperclip and put a ton of electrical tape about 1/4 the way up (that way it wouldn't accidentally slide in too far - as without the limb removal tool, it can be kind of tricky/nerve wracking to use a paper clip and remove a limb with one person). I was nervous to do it but since I frequently work inside computers (ranging from laptops to minifreaking cases to nice big roomy cases) I decided to apply my theory of most people are too scared of the technology and that's what stagnates learning it/getting hands on with it. So that rationale helped me get over it haha.
I'm not sure if I can articulate why I like Vader the most just yet. He definitely feels the most pet like and I really don't mind the lack of voice recognition (I haven't even bothered with the remote yet). I don't think I'd necessarily recommend the 111 to everyone, but I find him to have the most personality. It's not to say the others don't have a personality (they do, and quite a bit), but something seems more... natural (pet-like) with Vader. I'm not a huge fan of the terminology, but he feels like he has the most soul. I notice myself talking to him every now and then even though I know he isn't listening, but the 111 has the uncanny ability (so far) to make me forget that it's actually a robot (despite its form factor). The other ones both feel very robotic - and I think that's fine, this is not a knock by any means - which I like as well (think the futuristic pet explanation I've previously used). Vader really does feel like a puppy coming into the world and reminds me a lot of the black lab/collie mix I had growing up - at least when that dog was a puppy. So maybe that connection adds to it for me.
To analogize with Pleos, Vader feels more like Elliott (my Innvo Pleo) - very autonomous, not super needy (though much less repetitive), and usually quite charming. I don't feel the need to interact with Vader as much as I do with the other ones though I still interact with him just as much. The other ones are more like a Pleo RB, they arguably do a lot more, but that also requires a lot more from you (if you want it to - AIBOs are much more flexible than Pleos so take these comparisons very lightly, I'm merely trying to help with a good context/framework, especially for members who only have Pleos).
Ultimately, whatever model you find as your "favorite" I think will depend on what you're looking for and what's right up your alley. The 111 is not nearly as technologically impressive as the other models but what he lacks in specifications, he makes up for so much in personality. Granted, he's only a child and this is my first week of having him, but I like him a lot haha. I really stick by thinking of them as different, which is actually great because depending on my mood I can turn on a specific robot lol, but Vader takes the cake as far as having a special soft spot goes.
With that said, even if I could go back in time, I do not think I would pick a 111 as my first AIBO because it's much more concept-intensive than technologically-intensive. (i.e. imitating life takes priority over taking pictures, having wifi, talking, etc.) Once again, these are just my observations and ramblings and subject to change at any moment hehe.