Don't know if it will help you choose, but I bought one of these for my Nexus 7 (original):http://www.amazon.co.uk/Aluminum-Wireless-Bluetooth-Keyboard-Google/dp/B00AE3T5F4/ref=sr_1_4?ie=UTF8&qid=1377952526&sr=8-4&keywords=nexus+7+keyboard
These keyboards are really, really small, and may be okay for occasional use, but not sure if they'd be suitable for long periods of typing.
Anyhow, out of the two you've chosen, Keyboard A (similar to mine) will fit the Nexus like a glove and act as a good, protective hard, compact case/keyboard combination, but keys may be slightly closer together than Keyboard B.
Keyboard B will be bulkier & softer (more protective?) and the keyboards slightly further apart making typing that tiny bit easier.
If possible, I suggest you check these keyboard out at a store before buying - or buy them both and keep the one you like best & return the other one?