Cziffra's recording of the Grieg Concerto is sublime. I would pick the Grieg over the Schumann for first movement in a competition myself, but then again I'm biased; I love the Grieg concerto.
You know, the second I read the topic I prepared to post essentially this same set of sentences, exactly as it stands...but as Paul has done the dirty work I'll just leave it there.
Though, I'm curious about which recording you prefer. So far I've heard Cziffra/Cziffra Jr. and Cziffra/Vandernoot. Did he ever play it with Dervaux? If he did, I'd love to hear that, but for now I must say the Cziffra/Cziffra Jr. is my favourite. Plus, you can find it on a cheap CD with an equally prodigious Rach 2 with the father-son duo.
Michelangeli's recording comes close as well.
I personally wouldn't think twice about playing this at a concert (or a competition, although I strongly dislike competitions), even though I often DO have reservations about playing fully recognisable pieces (known more explicitly as "overplayed" pieces), the Grieg is just so incredible I feel it would be a crime to pass up an opportunity to perform it, as long as the pianist's interpretation is excellent. If that is the case, I prefer it to the Rach X any day.
I can't say I've given the Schumann enough time to grow on me, however; I'm currently not too impressed by the work, but have only given it a listen or two.