Wondering if a 640 core (from any brand) version is worth the extra money?

Do they actually deliver better images?

Yes and No! - More NO than yes too :)

Short Version - Longer Version in the Video

No if the magnification isn't enough for your purposes (remember they are nearly half the optical magnification of a 384 for the same size lens) then relying on the digital zoom (2x) just takes you to pretty much the same level as a 384 optically for a LOT more money ... - So clearly a NO

Basically if you need a 4x Optical scope; then a 2x Optical 640 with Digital Zoom to take you to 4x is just a waste of money, unless:

Yes if you want the Field of View and the same effective magnification as a 384 in the distance (by using digital 2x zoom) and the lower optical magnification level is fine for your purposes

Yes IF they have the same Optical magnification level as the 384 core - but this is a larger lens, more expensive, more weight ... then of course it will have better images

but its a yes with buts...

Any thermal is expensive - you need to look at what you need and intended ranges/detail required before deciding - Ignore any Detection figures quoted they are BS in the real world - look for REAL Images at REAL ranges if you want to see