I've tried three stylus types so far, with and without a screen protector (from an Otterbox Defender case, iPad Mini):
A generic rubber-tip stylus: the most sensitive, hands down. If you're in a "mission critical" setting and you're worried about your primary stylus failing on you, keep one of these as a backup. It provides the most resistance, whether on the plain iPad screen or on a screen protector. I worry every day that mine will rupture due to heavy use, but it's holding up so far.
A generic (eBay) mesh-tip stylus: excellent on a bare iPad screen, it glides much more easily than the rubber-tip stylus and the tip appears sturdier (although it still bends in just as easily). I need to use a bit more pressure when writing with it, but the apparent durability makes up for it. However, it doesn't work well with a screen protector.
An Adonit Jot Pro (dampening tip version): this gets a failing rating from me so far. Fresh out of the box the stylus wasn't registering on the screen regularly, with or without a screen protector. I contacted Adonit, who sent me three replacement tips at no extra charge (still waiting on them). In the mean time I tried the "thermal paste" fix and was rewarded with a day and a half of reliable writing usage, but then the stylus went back to registering irregularly on the screen even with cleaning and re-application of thermal paste. When it worked it was a delight to use, handling well and sliding across the screen (even with screen protector) very easily. Thanks to the tip type I also felt that I had greater accuracy and could write smaller (and thus, faster). But reliability is critical; I can't afford to have the pen stop registering with so many strokes (not to mention that it's an incredibly frustrating sensation, to write a stroke and have nothing appear). I wish I could say that this is a one-in-a-million defect but there are literally hundreds of complaints about this issue online. I will be thrilled if the replacement tips fix the issue, but the product was new and is one of the more expensive styluses on the market: this experience has been pretty disappointing.
Update: tips arrived, didn't fix the issue. Adonit support gets full marks from me as they are sending out a replacement part and will continue to work with me if that fails as well. I just hope the product can match their customer service.