The old N7 I would have said to go with the Sero 7 Pro, vs the new N7, I would say the N7 is better, LOTS better.
1. Screen resolution: The new N7 is a true 1080 p HD quality where the old N7/Sero 7 are 720p.
2. Processor Speed: New processor is supposed to be a LOT faster.
3. Internal Memory vs SD: Since Android 4.2, you CAN NOT put any app or any components of apps on the SD card, only media. This means, the 8GB you have on the Sero7 Pro is ALL you will have to install on (and actually, it's about 5.4 after the base install). I think the primary explanation is that SD cards are so unreliable because there are so many different types, that they can't count on them enough to insure stability so they just killed the option all together.
4. Updates - You really will want these: Updates are pretty critical because major new features require new coding to work with them and, as app developers want to take advantage of these features, they sometimes stop being backwards compatible. Being stuck on a device that gets really slow updates or non-existent updates can be incredibly frustrating. One example: A feature that will probably be important soon is the Chromecast API. Media apps written to stream to/work with the Chromecast. Say you want to be able to just stream from your tablet to your TV with the Chromecast from a video app. If the API support is in 4.3 and you are stuck on 4.2, you won't be able to do it.
5. All the features the S7 Pro had over the original N7 (except the SD Card expansion) have been addressed. HDMI out and Cameras have been added. SD Card support is a marginal improvement based on the lack of support for "Apps to SD" now.
Anyway, I was leaning towards picking up one of the S7 Pro but now that the new N7 is out and looks really sweet, it's actually worth the additional money.