I flew EVA and United Biz a couple times between US and TPE
Here's are my opinion -

Pros on EVA -
Can pre-select meals - up to 10 different ones to select
Service is pretty consistent - but sometimes a bit robotic
Seat is pretty private compared to united's 8-wide business class
Rimowa amenity kit
Bathroom is always clean, and the handicap bathroom is quite nice to change into your pajamas
All aisle access

Negatives on EVA -
While service is good, they tend to like to clean up the cabin right after meal service, thus, unless you ask for refills on wine/drinks specifically, they will just take the glass away.
Cabin tend to be a bit too warm for me - no individual vents if I recall
Everything is announced 3 times - English, Mandarin Chinese, and Taiwanese - aka long pauses if you are watching a movie.

Pros on UA -
Flight attendant are generally nice and happy to joke a bit - obviously I've been pretty lucky, YMMV.
Wines will be refilled until you ask them to take the glass away
Individual air vents to keep your area cool
I like the duvet on United better than on EVA

Negatives on UA -
8-abreast seating means sharing tray table, arm rest with your neighbor
Bathrooms are small
You'll learn to unplug your headset really quick when they start any announcement because it's 68% louder than whatever you're listening/watching


I have a few food photos on EVA vs UA earlier this year in April.
Everyone has different taste buds, I find fish is delicious on United. on Eva I prefer Duck, the pork chop is also okay.
I skip the sweets on both flights, so no pix on those but both offers plenty of cake selection to satisfy after meal sweet tooth.


EVA - LAX - TPE
https://imgur.com/a/ovGVC

United - TPE - SFO
https://imgur.com/a/mzMEy