That's exactly the phone I'm considering. I've pored through enough reviews on YouTube. It's definitely faster overall VS the Stylo 2. It's new enough (came out in April this year I believe, please correct me if I'm wrong, thanks) and is on sale some places, so I think I can splurge for this one. It's already on Nougat, so this phone should last long enough to get at least one OS upgrade. The other thing I love about the 3 is that the buttons are on the side! I can't tell you how much I love this.
My LG G Stylo is really beginning to age fast... I still have a Tribute, rooted with Monstro's ROM. That one still works way better than my LG G Stylo. That original G has already been randomly freezing on me for the last couple of weeks. I've even tried running it restored stock, and it's not fixing any problems, so I know it's time for me to upgrade. I've had mine for a year and a half. That's the longest I've had a daily driver recently! Anyway, I should be purchasing the 3 soon.
The only weakness for me seems to be the camera in low light. It does seem a bit grainy, but that hasn't always bothered me. Part of me will always be a film person at heart, so I know how to use grain to my advantage. Easy way to get the old school look.
My verdict, just spend a bit more for the 3! It's a real bargain if you're a gamer on a budget, but the rest of us deserve a responsive (and hopefully reliable) smartphone!