All right -- so which tablet is the right one for you? Putting it all together, I'd say this:
If you want a bigger display or a softer, warmer device, the Nexus 9 is probably the more sensible choice for your needs. And if having Lollipop right now is important to you -- and/or you value knowing that you'll always have the latest Android software straight from Google as soon as it's released -- by all means go the Nexus route.
(Side note: If pure Google software is your main concern, you might also consider the 2013 Nexus 7 as an alternative. Provided you're okay with a smaller tablet, it's going to give you a better overall experience at a fraction of the cost,especially now that you can frequently find it for under $200.)
Otherwise, I'd steer you toward Dell's Venue 8. It's generally the nicer tablet of the two, with a far more premium and high-end vibe that includes better build quality, a more impressive display, and more consistent performance. Throw in the exceptionally compact design, standout speakers, and option for expandable storage, and it's got the clear upper edge overall.
Dell Venue 8 7000 vs. Nexus 9: Which Android tablet is right for you? | Computerworld