Phil,
My decision at Riviera would depend on a lot of factors, primarily how confident I am in my driver at that particular time, but also my sense of how my opponent is playing, who's got the momentum, what condition my short game is in, etc.
At the Belfry, I just can't see any circumstance that would make me go for it in a one-hole playoff.
It's a wonderful match-play hole, and particularly so as a 10th hole -- a great spot in the match for a team or player to try to get back into the match, or put the hammer down. I think it would be a boring playoff hole in a stroke-play situation, however. Nineteen times out of twenty, I'll bet you'd see both players hit five-iron, wedge.