Which of these two (or something other I haven’t considered) holds up best through winter, used as a screen? Not worried about nutrition for wildlife.

Can't speak for Egyptian wheat but sunn hemp will be there until you cut it down or the deer eat the leaves, stalks will still be there. Sunn hemp will get 6-7' tall in 60 days

Good info!

I noticed my sunn hemp tended to not stand up straight into fall, because it flowered. But I had powerplant planted with it. It might work better as a stand alone if planted thick. Sunn Hemp grows an inch a day. My deer wear it out, but it grows fast enough they can't eat it down.

i have some of both seeds and am planning to try them each this year for screening purposes.

I've never grown sunn hemp, but here's some Egyptian wheat on February 24. It made a pretty good screen that lasted through deer season. It would have held up better, but it produced a lot of grain and the deer tore the stalks down when eating it.