I've been using the lg g flex for a couple of days, having previously been using a note 3 (and still issuing it).
Picking up the g flex is a joy. It's curved body and rounded corners, combined with an on/off button on the back make this so much more comfortable to hold than the note 3, despite the g flex having a bigger screen (and LG have improved on the g2 back buttons by having a texture on the volume keys so you know automatically where you are, though I found my finger naturally finds th, if I had to buye right position on the back). The note 3 now seems flat with a niggling shuffle needed to turn it on and use volume keys.
The g flex could have been more. The screen resolution is very good, and it's gloriously bright. However, the note 3's screen has more detail and depth. A resolution like the g2's would have made the g flex an out right winner for me. Reading on the curved screen took me a day or so before I got used to it (makes me realise how much we read from flat surfaces, and how that affects reading style). I like using the note 3's stylus on a slide keyboard, but using the slide keyboard on the g flex feels so much more natural due to the curvature.
Audio on earphones is very good, similar to the note 3 (though better, deeper external speaker). Video is more immersive on the g flex, though the colour and depth on the note 3 is brilliant, let down by the note 3's audio.
I haven't used the g flex camera much, yet. Though it doesn't have the g2's optical image stabilisation and at first glance the note 3 photos are more opulent.
The note 3 is a safer bet than the g flex. But a few days after using the g flex its ergonomic design makes it something I want to hold and use. Hats off to LG for innovation- if only they'd gone for ultra hd and included image stabilisation.
I've got the note 3 from work, so I'll be hanging on to it. But if the g flex had been from work it would have been a harder choice as to which to keep. And if the g flex had higher screen resolution it would have been an easy choice.
(Just played asphalt 8 on the g flex and note 3, same car, same course. The colours and scenery look rich and detailed on the note 3, and it's nice enjoying the scenery. On the flex g, the scenery isn't quite a rich or detailed, but the experience of driving is much more immersive. The curve and the feel of the flex making a big difference. I might hang onto the flex!).
Some additional thoughts:
-using the g flex on a flat surface to read is great, the curve tilts the text up making it easier to read
-when the phones are on a flat surface, it's easier to write on the note with a stylus than the g flex.
-There are many more features on the flex to make one handed use easier eg
*the soft control keys (home, back etc) on the g flex can be swiped to the left or right to make then reachable one handed
* you can put a fourth button on the soft control keys bar to bring down the notifications panel (on the note you have to reach to the top of the screen and swipe down, unless you use nova)
*you can make the pin entry panel on the lock screen smaller on the flex (the note only allows pattern entry to be made smaller, and since our corporate policies enforce pin entry it means I can't unlock the note one handed (unless I avoid the numbers 1,4,7)).
*On the flex, under settings, you can swipe from left to right to move from sound to display etc (on the note you have to press the icons on the top of the screen)
*the note does have one unique feature in the one handed stakes, however it's implemented poorly: with the right settings, if you swipe quickly to one side and then back the active screen shrinks and can be resized. However, it's fiddly, usually taking a couple of attempts. And worse, it's not persistent- if you turn the phone off and then on again the screen goes back to full size, undermining the possibility of bring able to take out the phone and use one handed. This is something that Samsung could surely fix easily.
-you can choose which apps the soft key bar should not be displayed in, so that you can get use of the full screen eg for evernote, games...
-the 'dedicated' memo button on the flex is very handy (press the up vol key for a sec or two)
So, if it was my money which would I go for? They cost the same on eBay; the note has a sharper display; the note is smaller and has a stylus (which I would use more on a tablet)- so overall, if I had to buy one or the other I'd go for the flex- it's a more enjoyable experience than the note.