Of all the first-turn MFi game controllers, I preferred the original SteelSeries Stratus. Not only was it the only standalone control option at the time, but its analog sticks and and overall design seemed to work pretty much perfectly for me. That being said, it was extremely small, which is great if you're looking for portability but not so much if you want a console-quality gaming experience. The SteelSeries Stratus XL changes that in a big, big way.
The most obvious difference here is that the XL is much larger than its predecessor. It's roughly as large as an Xbox One controller -- or the Wii U Pro Controller, if you have one of those lying around -- and as such it's immediately a good fit for anyone used to gaming on a console.
It has a full compliment of both face and shoulder buttons, along with a pair of analog sticks and a directional pad. The on/off switch is located on the rear panel and there's sync and battery level buttons on the top of the controller. As far as design goes, it's a massive improvement over the original, and feels like the controller we should have had all along.
My biggest complaint when reviewing the original Stratus was the fact that it felt cheap. The plastic housing, loose buttons and sticks, and lack of weight really made it feel like a toy. The XL is the exact opposite. It's heavy, solid, and everything stays firmly in place when you shake it. The analog sticks snap back upright with authority when you release them and I haven't noticed any of the issues that plagued the smaller version. In short, it's a ridiculous improvement.
Like the first Stratus, the XL connects via Bluetooth which means connecting it to your iPhone or iPad is as simple as venturing into the settings menu and pairing them up. I'm not a big fan of Bluetooth in general, and in an application as sensitive as a game controller, it's a bit of a crapshoot when it comes to latency, but if there is indeed any lag between the controller and the action on screen, it wasn't noticeably worse than I've experienced with game controllers on consoles.
If I'm going to really nitpick, I'd say that the shoulder buttons are a bit high to be super comfortable while reaching for them. The triggers, on the contrary, are perfect, but the shoulder buttons can be a bit of a stretch if you're in the heat of the moment. However, that's also an issue I've noticed with the Xbox One controller (I had no issues with the Xbox 360 controller, for what it's worth) so it may just be a personal preference.
At US$69.95 -- $30 cheaper than price of the original Stratus at launch -- it's the first MFi controller that feels like it was designed for gamers, rather than iOS users who happen to play games from time to time. Once you've played with it, there's really no going back.
SteelSeries says that all the feedback from customers, developers, and reviews was taken into account when designing the Stratus XL, and I have to say that it definitely seems that way. It's head and shoulders above the original -- and any other MFi controller on the market -- and there's honestly no better accessory for iOS gaming, bar none.