I have just purchased an iPhone 6+. I have given away my Galaxy S5. The last iPhone I owned was a 4 and things have improved so much since then. The 6+ IMHO is a very good device the camera is awesome.
The build quality is way superior to Samsung, no more clicky creaky hardware. IOS 8 is cleaner and less of jumble than Android and being free from Touchwiz is a blessing. I liken the usability, cleaners etc of IOS to that of Windows Phone.

As for the Thunderbolt plug a pleasure no more three times turn of the USB plug to get it in :)

As for the size, the device is a pleasure to use especially in the bright sunlight and actually being able to see the camera button in the sun a welcomed surprise, something that was invisible on the S5. The phone fits in my pocket and it's size actually makes it easier to get out of my pocket especially in the wheelchair.
The finger print scanner/unlock etc is the best I have used it is up there with that of the Huawei Ascend Mate 7, it takes a little time to set it up so it scans the entire finger print but the time spent is worth it.

Things that are on the downside for me...
The supplied power/data lead is too short
The new power adapter is hard to unplug one handed
The no back button taking a bit of time to get used to, I find myself trying to touch a non existent button.

All in all I would give the iPhone 6+ 9.5/10