We try to test on a variety of brands and devices. Thats a lot easier to do on iOS. Below are the devices we have on the Collector team that we test with regularly (and it is growing all the time). This doesn't include additional devices on other teams have such as the SDK teams or devices available through cloud testing services. In terms of a recommendation, theres too many factors to really recommend one tablet. With consumer focused tablets generally you're going to get higher end specs (better performance) because of the cost/time investment around developing rugged hardware. However the benefit for certain things like sunlight visibility, barcode scanners and operating temperatures (desert sun) can be really nice even essential.
I would start if you haven't already by listing your requirements (cost,specs,ruggedness,etc. etc.) and then categorize them by essential and nice to have and start seeing what devices make the cut. The question of capability comes up frequently when talking about android. Overall we see less device specific issues come through these days than a year ago.
This is solely my preference but I find the 7-9" device size is really nice in the field, the keyboard is bigger than a phone for typing, easier to hold than a larger device, smaller to shade if sunlight is a problem, bigger map than the phone, and still small enough for some pockets
iOS
We have every device Collector supports
Android
Phones
Galaxy S2
Galaxy Nexus
Galaxy S4
Galaxy S3
Galaxy Note II International
Nexus 4
Droid Razr Maxx HD
HTC One X
HTC DNA
Galaxy Note II US
Sony Xperia Z
Nexus 5
7-9 " Tablets
Nexus 7 - 2013
Nexus 7 - 2012
10" Tablets
Xoom Tablet
Toughpad FZ-A1
Xplore Ranger
Nexus 10 - 2012
Sony Xperia Z
Galaxy Tab 10.1 - 2011
Galaxy Note 10.1 - 2014
