Well, both OS are very different, one is a locked down simple OS, another is a flexible, customizable OS; it's not really fair to compare.
Comparing both OS, in terms of stability, smoothness, speed, WP surely wins, but it's restricted, little customization, etc. Both are very different in fact, WP is more toward iOS style but less restricted, more flexible and more customizable, more lively.
If comparing price, all OS have it's own value, and it also depends on the user. So, to Mr. A maybe they feel all OS are the same, and which one is faster means better, but to Mr. B, he maybe looking for a proper smartphone, a true mobile computer OS, in this case, it will be different story.
But anyway, there's no right or wrong, as long as the person is satisfied with the device. In terms of hardware and classification of the device though, the L820 should be mid-range which should be below S3, L920 should be the more proper competitor against S3.
Just like cars, there is different category and classifications, like B Segment, C Segment, D Segment. New generation cars are bigger, but it's still the same category/segment.
Oh ya u are right. But it's also not very fair to compare the price since S3 RM16xx is dealer price. If compare retail price, S3 RM1999 vs L820 RM1599 edi. But for dealer price, I believe it will take some time for L820 price to drop drastically.