We have serval Oce 318GL working here, OCE offer two kinds of ink, Flexible and rigid ink. Both inks show great color gamut, and very good adhersion, even on aluminum matereials. OCE 318 use Toshiba CA4 print head, 318 nozzles, 53.6mm width, Grayscale from 6pl to 42pl, 8 levels. It can print 4 point text with very clear edge.
The Oce 318GL have serval print mode, which you can choose per your job. The disadvantage is the speed, normally we are working at 6-7 sqm/h.
Regarding the CET Q series flatbed printer, using Richo GEN4, 382 nozzles, 32mm width, Grayscale from 7pl to 21pl, 3 levels.
So far as i know, the CET printer color is not as good as OCE printer. But their print quality is good.
Why not print your test file by both machines to compare, and try to check printer at customer side or consult some customers for advice.
Nicky