I haven't upgraded to the S7E yet but I'm seriously contemplating it. I really like my V10, it's a solid phone so it's a tough decision. I love the build quality, expandable storage, removable battery, IR blaster, double-tap to wake and the button placement on the back. Even the 2nd screen is more useful than I thought it was going to be, just wish the location was at the bottom.
What I don't like about the phone? Performance isn't great for gaming, it still has an LCD panel, the speaker is weak especially for calls, LG's UI isn't as good as touchwiz, the fingerprint scanner doesn't function reliably with a case on, and battery performance is dismal, which I guess can be forgiven since you can swap it out.
What appeals to me about the S7E? That awesome AMOLED display, great performance for gaming and the free VR Gear they give you, larger battery and solid battery performance from what I've been reading, they brought back expandable memory, the slim design of the phone even with a 5.5" screen, the edge panel seems like it has much more functionality than the V10's second screen, easier to theme than the V10, and Samsung devices tend to have better 3rd party support and customizations than LG phones do.
The V10 is a great phone and it will be tough to give up but I think the S7E will be a better choice in the long run.