[Xiaomi Mi CC9 / Mi 9 Lite Questions & Answers] seities:
hey. i've had both. i don't know about the band 28 situation so i can't comment on that.

Let me start by saying that I think CC9/Mi9 lite is a missed opportunity for xiaomi. It was positioned a bit awkwardly for marketing. It's evidently not sold very well and if xda is any indication, community support is also fairly low.

Yet to me it is the most "all-rounded" phone from xiaomi in 2019 (nope, not 9t/9tPro, which are very popular), checking off all the marks for me: samsung oled, great cameras front (better than mi9) and back, beautiful build and design of the Mi9, SD card, headphone jack, big battery, good battery life, midrange prices, etc. To me it was nearly perfect (except perhaps a year old SoC instead of SD730), or as perfect as I expected from Xiaomi anyway.

Except the fact it doesn't have strong community support. I've got it about 3 weeks after its China release. I am still waiting for official pixel experience or any AOSP rom to have stable releases. I am stuck with MIUI variant roms which are stable but I personally crave pure android. That and the fact there isn't a really reliable working GCam support, nor do I know of one in development (please correct me if I'm wrong).

This makes a huge difference because I shoot a lot with the phone cameras. Right now with GCam, I get more technically impressive photos from a lower priced Redmi Note 7 than the oversaturated painting I get from Miui's own cameras, and that's from a technically inferior Samsung GM1 sensor.

As it stands now, it depends on your usage and preferences. I personally wouldn't mind the Mi8 myself, especially if it's cheaper, except they are no longer available in these parts of asia (sold out). I think Mi8's faults are that the 845 isn't as efficient, and the battery is smaller, resulting in less run time. Yet it IS a flagship, which means potentially better build, better parts (it has a LRA vibration motor vs cc9's cheaper rotary motor), world bands gsm (where cc9 has a more regional bands selection), and more community support. The camera is an IMX363, same as on pixel 3 and 3a, so it's no slouch: while it has lower resolution on paper, it really just skipped the need of marketing driven pixel binning by having larger pixels to begin with. (Personally I think the apparent race toward higher megapixels as a strategy for xiaomi is completely misguided if not deliberately misleading). Post processing would be what makes or breaks the results, and with mi8 you can get full GCam support. In fact with pixel experience rom and gcam, you'd probably get nearly identical pixel 3 experience for a bargain. While 4000mah battery would be nice, pixel3/3a does just fine with similarly small sized batteries and oled. So it may just come down to better optimization.

oh, the underscreen fingerprint sensor is just crappy and unreliable. There's a reason why it's not as widely adopted. It's not a miss if you have the capacitive ones instead.

I personally would love a well supported phone, so my pick today might become mi8. As much as I love the cc9/mi9lite, it coming onto the stage too late in the cycle after all bases are covered makes it a bit of an orphan when it comes to development. I don't personally use the headphone jack but I would miss the SD card slot. Screens are similar, brilliant Samsung OLED. In fact I think Mi8 was touted as one of the best displays from Xiaomi in terms of color accuracy. If you don't care as much about community support/aosp roms, and is content with MIUI and its camera app, then CC9 is really as good as they come this year. From the way the new xiaomi phone looks (redmi k30, cc9 pro, rumor of mi10), such thoughtful and balanced design is probably going to be a rarity in the up coming models. :P

Hope this helps