@Jimbotron:
They're updates to the previous UX305UA thus almost identical in terms of chassis design and components. Whichever one you decide to go with, make sure to check for a 7th gen Kaby Lake CPU since there are models with the last gen Skylake as well. Kaby Lake models not only have better battery life and minor upgraded components, but also fixed lots of reported hardware issues and bugs, so it's more than just a small update. (Unless you want to install an older Windows OS, which I believe isn't possible from Kaby Lake onwards.)
Now as for differences, here's what I can tell.
- As you know, UX360UA has a reflective glossy screen, and UX330UA has a anti-glare matte screen (Though just like phones and tablets, there are some decent aftermarket matte, anti-glare screen protectors. These also help with fingerprints and smoother touch experience due to the film being plastic, not glass.) If you don't have experience with both, don't try to guess what it's like as general opinion is very polarized. Some prefer matte due to the less reflective aspect while others actually enjoy glossy due to more vibrant colors. I highly suggest you try out either or both in a store. (though not Apple store b.c Macbooks are glossy + anti-glare)
- Their Full-HD IPS screens both have around 340 nits of brightness, 90% sRGB 60% AdobeRGB color coverage and issue of low frequency PWM (which I heard could be controlled via software). Difference lies in contrasts and black levels. UX360UA has 1269:1 contrast ratio whereas UX330UA has 1636:1. That's quite a difference since contrast is the most noticeable aspect on an IPS screen for an average user.
- UX360UA has a full HDMI port whereas the UX330UA has a micro-HDMI port so needs a converter dongle for use.
- UX360UA has dedicated volume buttons, a long vent grill, and its power button all on the left side. UX330UA has no volume buttons, no vents on neither sides and its power button is positioned on the top right corner of the keyboard where an End or Delete key would normally be on a US key layout.
- UX360UA has an option for a fingerprint reader, UX330UA does not.
There're no performance differences, except these laptops are comprised of storage from multiple manufacturers. Storage is the slowest part in a PC so with bad luck, this could be noticeable but only if you care enough to notice it.
I would personally choose UX330UA because I need anti-glare and a 2 in 1 laptop without an active pen and aftermarket pen support for me is unusable.
Hope this helps.
Source:
https://www.notebookcheck.net/Asus-Zenbook-Flip-UX360UAK-BB351T-Convertible-Review.198302.0.html
https://www.notebookcheck.net/Asus-ZenBook-UX360UA-Convertible-Review.181132.0.html
https://www.notebookcheck.net/Asus-Zenbook-UX330UA-Notebook-Review.182710.0.html
https://www.asus.com/Laptops/AllProducts/