I have a Samsung Tab S2 and a home built Stratux with gps and ahrs capabilities, and no panel gps or AP, so interfacing with avioinics is something I can't address. Started with Avare a few years back, then moved to FltPlanGo which worked well. I would have stayed with it, but at the time it didn't support ahrs input and I wanted to get the most out of my stratux, so I downloaded iFlyGPS and used it free for the trial period. Subscribing afterwards was a no brainer. Works great, very easy to use, map update functions have been streamlined and are now excellent, flight plannning is so easy and intelligent with it that I don't find it necessary to use a computer at all anymore, but it does fully integrate with 1800wxbrief.com. You can easily get full certfied (or whatever the right word is) briefings, although a few of some of the graphical products come up as web links. You can file and store flight plans. EXTREMELY customizable display...you can see what you want to see, how you want to see it, and where you want to see it. Synthetic vision, ahrs or gps derived backup six pack...terrain, obstruction, traffic, time--to-descend alerts and many others configurable... and all easy to learn to use and easily accessible without having to be pinpoint accurate with your finger while in bumpy air.
Two minor drawbacks.... the lack of checklists, user-designed or otherwise. I liked and used that function in FltPlanGo. Also, no W&B calculator. I've asked them about that in two occasions over the past year or two. Earlier response was that they focus on navigation (and they DO do that exremely well), more recent response is that those things are now on their short list and are working on them.
Another plus for the company is that they are very responsive to their customers. Emails are answered sometimes even within the hour, and it's easy to get someone on the phone. The company is also growing quickly...personally, I'm not sure that's a plus or a minus, but so far I'm a big fan. My CFI is a diehard FF fanboy, and is constantly showing me "but FF can do THIS..." ..so far, other than being able to display faa publications like FARs, various handbooks, etc., he hasn't shown me anything I can't do with iFly on an Android....and I can easily view those documents outside iFly, so that's not a concern. For hardcore ifr pilots needing features I might not be aware of and/or Apple fans, PERHAPS iFlyGPS might fall short somewhere....but I can't imagine where. Great app, designed by pilots for pilots.
I have NO ties to the company...just a satisfied and impressed user.