I wouldn't think performance would be the top factor for people who choose a masonry heater anyway. In terms of performance, you're making a heater out of something with (relative to steel) very poor thermal conductivity but very high thermal capacity in order to overcome short burn times- a problem which a couple modern stove companies have overcome anyway (BK, IS).
Not saying masonry heaters can't heat a house very nicely- but they trade thermal conductivity for thermal capacity. If I didn't have a BK I would probably be asking why everyone didn't do that.
In terms of aestheticics, though, there's some jawdropping masonry heaters out there. I don't usually even remotely care how stuff looks, but I've seen some that made me go 'WOW'.
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The coolest wood stove on the internet. In addition to its looking cool, the big glass surface area probably allows a lot of radiant heat, which ought to help with warming up a cold house in a timely fashion.