Nissin released the i60A about one year ago and has slowly made a name for their brand as a flexible and reliable flash and trigger option for all major camera manufacturers.
As you can see in the size comparison between the Nikon SB-700 and the Nissin i60A, the Nikon is a bit beefier/chunky and weighs slightly more. The Nikon also has a zoom range of 24-120 while the Nissin i60a has a range of 24-200mm. Light output compared to the Nikon SB-700 and the Nissin i60A will be forthcoming using my Sekonic 858, as well as flash duration. My experience says the Nissin may have the edge, but the test will tell the real truth.
What makes the Nissin i60A such a great flash? The flexibility of the i60A to be used with almost any camera brand when the camera body is paired with the Nissin Air. This means you can use your Fujifilm XT-2 with this flash, even though the mount is for a Nikon and vice versa - because the flash has a built-in receiver that pairs to the Nissin Air regardless of which camera.
The design of the Nissin i60A takes a different approach - where most of the electronics live in the head, while a traditional flash has most of the electronics in the body. I am not overly excited about the Nissin i60A's design approach - especially if you are using MagMods which make the head more top heavy and has a tendency to drop down when modifiers are attached. But the design does allow for a lower profile - if that appeals to you.
The one design issue I find is the battery door - which is spring loaded, hinged and when opened the hinges extend which make it a bit tricking to close plus the battery door can open accidently when adjusting the flash if you hand moves it slightly.
Yes, the Nissin i60A is remote off camera and compatible with TTL and High-Speed Sync if your camera supports it. Nissin has recently announced a new Air commander Air 10s which makes this an even more attractive package if you purchase them together.
The Nissin i60A does support automatic control from the Air Commander at the camera location + automatic zoom control, not to mention full manual control as well if you so choose too.
My recommendation: If you are just starting to get into flash I would highly recommend you take a look a the Nissin line - if you ever change out your camera body from one manufacturer to another this Nissin flash will continue to work with your new camera when paired with the proper Nissin Air commander, good news is the Nissin Air Commander is not all that expensive. I have used this flash with both my Nikon and Fujifilm with very good results in both manual and automatic TTL modes + HSS. Thus, it would be a wise choice for anyone starting out in flash.
I should also mention, with a Nissin trigger you can use your Nikon flash alongside the Nissin Flash in fully automatic or manual modes - independent of each flash when on separate channels.
Question and Answer Time:
Q. Can I use a Nissin Air Commander on my Canon/Fuji/Sony body and control a Nikon Flash with a Nissin receiver attached?
A. No - The system is not cross-platform compatible. However, you can use an i60A Flash (regardless of camera mount) with any camera body - as long as the body has an Air Commander attached. Example: Buy an i60A with a Canon mount - and use your i60A off camera with a Nikon & Air Commander.
Q. Can I use an i60A Flash alongside a Nikon SB-700/910/5000 Flash if the Nikon Flash has a Nissin receiver attached?
A. Yes, As long as the Nikon Camera Body has a Nissin Air: just remember, the Nissin i60A will work with any Camera Body but Canon Flash only work with Canon Bodies, and Nikon only with Nikon bodies, etc.