Sorry i wasn't clear in my post, I was refering to buying the group on aliexpress according to the subject of this thread.
What i had in mind, complete 105 DI2 :
https://fr.aliexpress.com/item/1005005024569017.html
The buyer mentionned by @Bassa80, this isn't full group, just electronic parts, so you can customize the rest (chain, crankset, cassette):
https://fr.aliexpress.com/item/1005005766195381.html
Thanks for that. So, if i were to pull the trigger now, shipping to Romania, there'd be a 200 eur diff apples to apples between ltwoo er9 & 105 di2, 400 vs 600 eur (after off the shelf coupons).
Shipping to France, difference is smaller, but that would justify digging more into other listings, as the er9 would cost 470 eur, and i'm not paying that much for an er9 group.
Perimeter: electronic bits + calipers.
I attach little to no value to shimano crankset, rotors, cassette and chain, so for me it's great to have the option to only order the electronic bits.
I'd probably go with shimano, because having done 13000+km on er9, i'm curious to see how di2 behaves.