It’s awesome that there are so many excellent pressure-sensitive pens available now. Air Display 3 supports the latest from Wacom, Adonit, Adobe, Ten One, and Fifty-three.
For my money, the best of the lot are both from Wacom: the Intuos Creative Stylus 2 and the Bamboo Fineline. Each has its advantages. Both have a solid heft in the hand, fine tips, and are shaped to stay on the table without rolling off. (Believe it or not, most of the other options roll off if you aren’t careful.) Both are priced well. The Bamboo Fineline has a cheaper price point and finer tip, but has a sort of flimsy plastic clip on the cap. The Creative Stylus 2 is more solid. You could use it in battle. And it has two side buttons instead of just one. It comes in a precious little case with extra parts, just in case. (No pun intended.)
On the other side of the scale, you have Adobe’s embarrassing Ink. Ink has the most attractive shaft, but that’s its only positive point. Ink is actually an Adonit Jot Touch with Pixelpoint with the name crossed out and Adobe Ink written over it in crayon. (Well, figuratively.) But at double the price. And as a little googling will reveal, the battery tends to just stop taking a charge after a few uses. Fortunately we found that Adonit will replace Adobe’s dead styluses promptly and cheerfully. (But isn’t it curious that you buy it from one company and have it replaced by another?)
Fifty-three’s Pencil is a wonderful device. I love it. But it’s not a pressure-sensitive pen, despite what its marketing and pricing might have you believe. Their app just does a great job of faking it. Pencil uses Bluetooth LE, but only for palm rejection and to discriminate between the stylus tip and the eraser. And there’s no modifier button.
On iOS 8, you can simulate pressure with the Pencil by varying the angle of contact, but if that works for you, just use your finger! iOS 8 allows app developers to discriminate between small touches and large touches. So if you can vary the size of the contact, Air Display 3 can change the “pressure.” So I’d recommend your finger over a Pencil.
I’ll just point out that, the above pigheaded opinions notwithstanding, the worst pens of the lot are still amazing feats of engineering. You can’t go wrong. But with the latest Wacom pens, you can get something kind of incredible at a nice price.