I'm very, very picky when it comes to phones. Currently, I can't find a single phone that I love, and only a few that seem half-attractive.
What I want from my phone: Great battery life, smoothness (lag free), customisation, quite a lot of apps (ie, Android or iOS), a good display, and an amazing body.
The phones that currently appeal to me are the OPO, HTC One M8, iPhone 6 and the Google Nexus. I'm currently using a BlackBerry Z10 and never have to worry about battery life as I switch batteries all the time, and never plug my phone in charge because I have a battery charger. (ie, one that I insert the battery in).
BlackBerry 10 is pretty solid but I can't stand the ocassional lag, lack of customisation and the lack of important apps that I need such as HSBC. (it has a terrible Android port). I also hate touchscreens. The BlackBerry 10 keyboard, no matter how "great" it is, just isn't good enough. Neither is autocorrect. The only thing I HAVEN'T thoroughly tried is Swype. I tried it a bit and hated it, but I'm willing to properly test it.
Ah yes, the reason I included the iPhone 6 in the list is because it becomes a beast after jailbreaking. And because when I was younger I fell in love with this theme called BladeHaz3 HD. (I believe that's what it's called). My Dad's extremely happy with his Samsung GS5 but I can't understand how you can stand a phone that's even a little unresponsive or buggy, and that has so many unnecessary gimmicky things.
My friend has the OPO and her music player has been acting up lately (and wasn't fixed by a restart) so I don't know...
The only problem I have with my OPO is the zoom function breaking. It fixes with a restart but it happens pretty regularly so you might want to avoid that. The body is good, it's extremely customizeable, you have the play store so there is of course a large variety of apps, and the battery life is great; it seems to last a day and a half. The screen is a 5.5" 1080p IPS and looks quite good.
So other than the occasional bug, the OPO basically fits.
If you're looking for fluidity, I would look into the iPhone. A few years ago I was big into Android, but then I switched over to iOS and I liked it so much more than Android. (iMessage, seamless connection to my computer, fluidity, ease of use, etc). I have an iPhone 5 right now and even though it's two years old it can hold its own, and will continue to for another year or two I assume (and it still has good re-sale value). I haven't found it to be buggy at all either.
Anyways, I've tried out the iPhone 6 & it's just buttery smooth. All of the apps launch extremely quick and the battery life is not bad with LTE on. I would assume that not being able to swap out batteries for you would be a pain though, considering what your current situation is right now.
Well all android devices have a lag, not as much anymore but it's just something about them that gives that lag no matter what, but that's been well covered. iPhones are basic, good looking and lag free unless doing heavy tasks and windows phone is also lag free and can do heavy tasks, but there's no apps.
Overall though you probably want an Android device, the lag can be minimal these days if you get the right one, for example, you wouldn't want a One plus One or an LG G3 just because of the increased lag.
Maybe a Nexus 6 or that new moto g/x or whatever it is that just came out.
What OS are you running on the Z10? I have a Q10 with 10.3.1.1154 and it's been very lag-free. The only time it hangs a bit is right after a boot when everything is loading up. Otherwise, it's been a solid leak. Also, you can download the actual Android APK for the HSBC app and install that rather than the BBWorld port. As far as customizing, yeah, BB10 hasn't had the theme support like the legacy BBOS's; but I never cared much for them anyways. I'm perfectly fine with just having a custom wallpaper and lock screen.
I know it's a weird phone, but maybe check out the Passport? If it had come out on Verizon I would have gotten one...
Dont go with the g3. It is really meant for 1080p as in the adreno in it. The g2 is exactly the same minus 1gb of ram. So the 32gb g3 has 3gb of ram and a 2k screen. The g2 has 2gb and 1080p, for me I cant notice the difference between the g2 and g3 displays (owning the g3). I love the display, for video it is phenomenal. However gaming it actually lags at times. The g2 doesnt experience the lag because the g3 and g2 share the same gpu (adreno 330) and slightly differing cpus (only difference in speed). Its snapdragon 800 vs 801.
Go with the g2, the biggest use with either or is the ir blaster. Honestly if you wont ever play higher end games go with the g3. Otherwise go with the g2. The games I cant play on it are the anomaly, shadow gun, modern combat, etc. It lags severely at times in all of them with my g3.
The 2k is bad for one other reason, it over heats so much when you watch video for a long period of time even with the brightness slightly lower than max. The g2 I would guess doesnt get hot on full brightness like the g3 does even when just web browsing and not watching video (gets much hotter at a quicker rate with video on full brightness). I love it, but the display honestly sucks. Go 1080p or with the note 4, otherwise wait for better 2k ones.