HUD vs EVAS
Got both on the jets I fly. HUD is absolutely no help if there is smoke in the cockpit. The HUD produces an image that is created by a projector mounted above and slightly behind the pilot's head. The image is projected onto the combiner (screen) in front of the pilot. Thick smoke would obscure and dilute the image - it would never reach the combiner. Even if it did, if the pilot leaned forward to see the image his/her head would block the projection.
EVAS works. If the aircraft is flyable and you are able, you can fly and land with it. I've practiced it in the sim; filled the sim with smoke to the point I couldn't see the copilot but I could see the instrument panel and outside through the window.
I did not see UPS mentioned on the EVAS website as a user of their product.
Best,
GC