Just read a review of a Nexus 10, it's screen is even better than an ipad.

http://www.t3.com/reviews/google-nexus-10-review

The gf has a nexus 7 and it's a pretty slick.

I saw a test that said for viewing photos the kindle fire was better than the ipad mini and the nexus came in last

from using the both the ipad mini and nexus 7 the nexus has the better screen - apple seem to almost have neglected the mini's screen definition.

i own a nexus 7 and have played around with the kindle fire hd now as well.
In the real world there is no particular difference between the two in screen quality, if anything i'd say the colouration from the nexus was more natural but it's a very slight difference.

For displaying pics for a portfolio i'd be looking at something a bit bigger like a nexus 10 or ipad which both have a high pixel density and good screens.

commercially, Ipads seem to be the default when vendors want to show us something flashy, never seen one use and android tab yet

Doesn't one of the newer tablets have the option to run multiple accounts? Could be useful if you're sharing it.

*Double post edit*

And if you like the idea of being compatible with your Windows devices you might consider a Surface [url= http://www.microsoft.com/Surface/en-GB ]Microsoft surface thingy[/url] or similar from the raft of Windows devices that are coming out at the moment

Just ordered a Nexus 7 for mrs Taxi for xmas. I don't know anything about them but was recommended one by a friend.
Only thing, I forsee a problem you might have.
"So I have decided to get a tablet for myself and my gf to share."
That is never going to happen ! just give it to her as soon as you get it and start saving for your own.

I have an iPad 3, which means I have the retina display. I know you didn't list it as one you were interested in, but for show casing photographs I cannot stress how good the screen is. I use mine to download the contents of my SLR after a shoot, and for backups while on Holiday and love the screen. The image quality is unlike anything I've seen before.

The iPads all work fine with any PC, as long as you can run iTunes you can use the iPad, no problem.

The iPad is truly fantastic, as a web developer I've even known to be sat in Starbucks writing back-end code on mine, without any issues.

If you have any specific questions, feel free to ask 🙂

I have tested most of them for work and to start with don't worry about the screen quality. They are all good enough and you really don't notice the difference. Its just a talking point for geeks. A bit like megapixels with digital cameras.

You wont have any compatibility problems with iPads or any of the devices.

Microsoft surface is a great idea but it runs slowly, takes 5 seconds every time you want to open an app which doesn't sound much but gets really annoying. The keyboard however is amazing.

Kindle and Nexus are great but seem quite basic and there isn't the range of apps for them. This might not be a problem for you but worth checking what portfolio apps there are for showing off pictures.

Personally if you are using it for business I would go with a iPad. iPad mini is great but g for an iPad 2 if showing off pictures. Hardly any difference between the iPad 2/3 and now 4.

Best idea is to order all of them over the internet, give them all a try and then send back for a refund the ones you don't get on with. Remember with mail order you have 7 days to return an order. Most companies however give you 14days to notify them.

[url= http://www.displaymate.com/iPad_mini_ShootOut_1.htm ]Screen shoot out Nexus vs Fire HD vs iPad[/url] - Hint iPad loses

I've got a note 10.1, it's great. I like the way I can scribble over everything . Great for working on , and you're not restricted to what Apple says you can or cannot have.

Just read a review of a Nexus 10, it's screen is even better than an ipad.

Err except in colour gamut, which is a fraction of the iPad...