Being on my 2nd set of the oval type, I would gladly take the round ones because the casings on the ovals corrodes very badly. Back when Airstream covered this under warranty, they replaced mine, however the second set, 3 years later, is worse now than the first set was after about a year and a half.
If you have the choice, the rounds materials seem to hold up better. I've seen a fair number and none had anything close to what I've seen on two sets...
Computers manufactured by companies such as IBM, Compaq and millions of others are by far the most popular with about 70 million machines in use worldwide. Macintosh fans note that cockroaches are far more numerous than humans and that numbers alone do not denote a higher life form. -NY Times 11/91