I think the choices, other than Polar, are Sigma, Cat Eye, VDO, and Suunto.
I wouldn't let the aesthetics of the sensor influence you. Most people won't notice, and of those who do, they'd probably be more impressed by it.
My older Cat Eye has stood up, and I'd consider another if they had PC connectivity, but they don't. The Sigma is the cheapest of the remaining three, with a good reputation, so that's what I'll probably get. The VDO looks interesting, but I haven't found any justification for the higher price. The Suunto has a really neat, modular design philosophy, but its even higher price is the factor against it. Unfortunately, none meet my needs entirely, so I may get a separate heart rate monitor instead.