We can all agree that Chihaya from the game is flat, but way more likeable than Xenoglossia Chihaya. 
Agreed.
The B72 Chihaya is cute and adorable (and technologically inept); the busty Chihaya, on the other hand, is just a psycho who is romantically (and possibly sexually?) attracted to 30-meter tall giant robots... -__-;;
Honestly, even though I liked Xenoglossia, I still couldn't bring myself to like the Xenoglossia Chihaya.
(However, I did love the mecha designs in that show, especially Ziehdraht >w< )