And here we go with another 5.4 bashing thread.
The 2014 is the last year of the 5.4, and yes, you will need to do the timing job and roller follower job between now and 150-160k miles. That said, once that job is done, the engine will be reliable for another 150k miles, especially if you take care of it. If you're mechanically inclined, you can do the work yourself for about $1500 in Ford OEM parts, regular garage tools, and a couple of specialty tools from Amazon. Is the 5.4 a fast engine or as powerful as the 3.5 in the 2015-2017 models? No, but is also doesn't have any potential turbo related issues.
To answer your other questions:
Transmissions, drivetrain, and 4WD systems are the same between 2014 & 2015-2017 models. Interiors are the same except for colors. All drivetrain systems should be serviced regularly since the "lifetime" fluids do wear out and maintenance is cheap insurance against failure.
Telematics and instrument cluster are updated on 2015-2017 models, with two cluster designs (trim dependent) and Sync3 with touchscreen and updated navigation systems. That said, don't let the infotainment system be a driver in your decision since they fall quickly out of date and support. I believe the 2015+ models can be upgraded to Apple CarPlay with a USB module swap. 2014s and lower require an aftermarket head unit swap for CarPlay or Android Auto.
Either model is reliable as long as you take care of it. Don't run away screaming from the 5.4 unless it has notable ticking, chain slap at startup, or other odd noises an engine shouldn't make. Note: the 5.4 injectors tick loudly, but that's normal. Odd noises will come from the front of the engine or under the valve covers.