Have you made your choice yet Tom?
I know, this is an old thread, my apologies for not responding earlier but I hadn't tried both the devices out yet and didn't have anything worth while to say about the comparison between the two. Now I have a couple of both kicking around and have a decent amount of hands on time to compare the two. The biggest question in my mind for which is better for your kids, how old are they?
Durability- the Nexus 7 is a very well built tablet, and the softer backing they have has saved my middle children from broken devices more then a few times not to mention it is much easier for excitable kids to hold on too versus the run of the mill typical plastic/glass/steel backing. For kids in the 10 and up range with at least moderate care(kids will always be kids) the Nexus 7 should hold up quite well.
The Nabi 2- I guess I could try and drive the minivan over it? The bumper on the thing may not look like all that much, but I just don't see how a kid could hurt the device. The bumper is even food grade plastic(in other words, safe for kids to chew on for those without little ones). Once you remove the bumper it is likely as damage prone as the Nexus 7, perhaps moreso, but there just doesn't seem to be a good reason to remove the bumper. Even if I grab it to look something up online for a few minutes when the kids aren't using it, I leave it on. Sure, it isn't the most image sensitive thing if you are worried about carrying it around in public with you, but it doesn't intrude on the functionality overly much(although I would likely permanently remove it if I were going to use it for myself).
Usability- The Nexus 7 is pure Android as to be expected. Easy to handle the basics, tweaks beyond what a single person is capable of doing in their life(that has its' own pros and cons of course). Not a lot to say here as it is what it is and so much has been written about it there isn't a lot I could expand on.
Nabi 2- Very simplified UI out of the box. Requires a setup by mom or dad and then defaults into the Nabi's custom UI. A grid of 8 icons per page, with plenty of pages to scroll through. You can make the icons a folder, move them around, open up the app drawer(an odd location, on the right hand side in a little grid) to move apps around, change the background(*very* limited out of the box). There is also a parent mode, and this is pretty close to vanilla Android. From here you have access to the normal Android functionality- can install the Amazon App store easily(a must IMO) and some special features for administration of your child's Android device.
This is one area where the Nabi 2 just kind of plays a game noone else tries. You could install all the most vulgar/violent games in the world on the device using Mom/Dad mode and your child would never know unless you go into a separate app and select for it to be able to be seen by your child. You control each and every app your child has access to. You also have a choice between different browsers, the default one being *very* restricted but which allows you to add URLs of your choosing that you deem safe for your child.
There is also a sort of 'friends circle' feature built in to the Nabi2. You control this from your parent dashboard(you can access that on your PC/Mac via a website or directly from Mom/Dad mode). You can add a list of people that your children can communicate with on the Nabi 2 directly and via email- siblings, parents, grandparents etc, and the Nabi software will make sure your child only sees emails from those sources and can only send them to the same.
In terms of a parent buying a tablet for their child and wanting to keep them in a safe environment, it's a boxing match between Mike Tyson and Pee Wee Herman- it isn't remotely fair to compare devices as noone else is playing this game at of the big hitters.
Raw hardware- Nexus 7- you know the deal on that one
Nabi 2- My wife summed it up best- "my four year old's tablet wipes the floor with mine". Honestly, it seems like ludicrous overkill, but you fire up Riptide Tegra3 build and see it playing so buttery smooth and it really hits you how overpowered this is for the typical childrens applications today. Hopefully, this level of hardware will give developers a chance to throw some nicer applications into the market for the younger folks. If this came at a significant price premium I would say it wasn't worth it, but the fact that it comes in a $200 package? Maybe someone could argue against it, but it wouldn't be me. It is nigh a Nexus 7 hardware wise, the screen isn't quite as good, it's a bit lower resolution and off angle viewing certainly isn't as nice, but on angle it is hard to tell the difference in most things honestly. SD card slot, HDMI out- the Nabi 2 seriously seems like overkill, but the thought that the kids aren't going to outgrow this anytime soon is rather comforting to me honestly.
App availability-
Nexus 7 has Google Play. Nuf said.
Nabi 2- by default, ouch. There are some apps aimed at very young children, and that's about it. You can feel good knowing that they are safe and not have to worry about them grabbing something they shouldn't. Amazon App store is not only allowed, they nearly hold your hand to install it on the Nabi 2 which solves a lot of problems. Is it Google Play? No, honestly it is a fair bit behind. But it does give you access to tens of thousands of apps, including a lot of the most popular, which you can install and decide which your children should or should not have access to.
Misc- Nexus 7 seems better off in terms of battery life. Nabi2's buttons can be picky due to being under the bumper. The ports on the Nabi 2 aren't covered so they aren't immune to PB&J.
Chores! Nabi 2 has an application for tracking chores. You can buy coins in Mom/Dad mode using real money which would allow your children to purchase titles on the Nabi 2 app store. You can tie the awarding of these coins to the completion of their chore list. Very simple idea, aint gonna lie, I love it, freaking ingenious.
Foozkids- linked above in a post from almost a month ago, hard to explain. I don't have enough time yet to give you a verdict on it, but the idea behind it is stellar. Your kids take part in app based education and are given awards based on their progress and work. You have to pay to join up for the advanced features, and $70 a year may or may not be worth it, I'll have to get back on that after some more time, but the idea is something I am a huge fan of.
Overall, IMO- 12 and up- Nexus 7- don't second guess it for a second. 8 and under- Nabi 2 and don't bat an eye. 9-11? Judgement call.