Hey hope I can help you some! I've had both the LG G5 and HTC 10 and I can give you my thoughts!
I got the G5 when it was available for preorder. All the stores and stuff about the build quality erked me a alot. Made me nervouse. Then my phone arrived. It was completely fine

No gap. No imperfections.All was good

I had silver. I liked it alot

Very fast and fluid and loads apps very fast. The camera was amazing. I kinda thought the wide angle camera was a gimmick...untill i used it. Man I miss it so much. Every smartphone needs to have this. You dont realize how nice and convenient it is till its gone. Also a fact, the T-Mobile Variant has root now. Okay back on to my opinion. The buttons were very sturdy. I though build quality was very good. It doesnt feel like metal but I think metal is over rated especially if your one to use cases. You never really feel it and plastic doesnt give you the bending problems like metal does Cough* 6P Cough*.
On to the modules. Please do not get this phone for the modules. Only look at the modules as a means for swap-able battery and that's it. With only 2 modules out and probly the only ones ever to be out not to mention only 1 in the USA. I was interested in the cam plus but there seems to be issues with it. Make sure u buy it from your carrier as the network bands are in the bottom and might say incompatible if u buy the wrong one. Also Ive seen reports over it not charging the phone when attached. This might just be a defect not sure.
Also theres new reports that LG did usb type c the right way in that it supports qualcomm quick charge 3.0 and USB power delivery. So its all up to specification unlike the HTC 10 which doesnt support Power delivery. The phone does get warm. finger print scanner is one of the best. Works just like the HTC 10 and 6P.
The screen is good not amazing. Its not amoled. But a very good LCD. The HTC 10 lcd is a little better. The G5s screen isnt bad though its very good just not the top LCD panel. No adoptable storage on the G5 unlike the HTC 10 but I dont really like adoptable anyway since it encrypts your storage and is only readable on that phone. So if you pop it out and put it in ur computer it cant read it.
Now on to the HTC 10. Let me just say this. This beast is Rock Solid. I've never felt a phone more solid than this. Its metal and you can tell. The screen is very very good. Amoled like. Both the G5 and HTC 10 have good screens but the 10's is better. A little brighter too. Buttons very very sturdy. Fingerprint scanner is very good, its had some misses lately but might just be a fluke.
The speakers....I don't think there anything special. Yeah there's two but there just not super loud. The G5 has very great speakers for only having 1. Id say the G5s is a little better actually. Speaking of headphone sound though the HTC 10s is one of the best hands down. Phone does get warmer than the G5 though at least to me. Very very snappy. No lag, not that there was on the G5. Battery life is averaging me 4hrs sot almost same as the G5. Maybe better by 30-40 minutes but the G5 does have the swappable battery so you decide what you'd rather have.
The 10's camera to me was lukewarm. I know its capable of more but the processing and software just isnt there all the way. And I think they cheaped out on the coating on the camera cover because I've never had problems with lens flare like I do on this phone and cleaning it. Just seems like there's no oleo-phobic coating(sp?) like on other cameras. I've never had to clean or wipe it off as much as this. It really drives me crazy. The camera seems to not have the best dynamic range. Exposure is also wonky unless you use pro mode(manual controls). Tap to focus does not adjust exposure like other cameras. It also does not do spot metering, exposure just adjusts the whole shot or frame. I don't like this. Also exposure on the front facing cam doesn't adjust to your face very good in a dark room (it adjusts to the background a lot). OIS seems to do a little bit better of a job on the 10 over the G5.
I will say this i will take the G5s cams any day over the 10's no matter if there are updates to the 10's software. Its just better on the G5. Focusing on the 10 seems to mess up alot or be wonky or just slow compared to the G5.
Also, if your buying the HTC 10 Unlocked from htc.com you will get updates very fast. If not you will get them the same speed as the G5 since the 10s and G5s from carriers will be slower since the carriers have to modify and approve them also.
I returned my G5 2 weeks after because things just bugged me and I like to change phones alot and I was in the return policy but Im returning my HTC 10 this week and rebuying the G5. The 10 just doesnt wow me. All it seems to have going for it is build and stock feel. Ill take the G5s cameras over the 10 anyday. Hope this helps. I know its a long read but this is my Honest Opinion.