The Shield is not better. The Shield isn't even a poor man's The Wire.
The Shield uses the standard cops are selfish bastards in it for themselves, adds some gay sex scenes, some pranks involves faeces and suddenly it's a brilliant cop drama.
The Wire was way more original and so much more real than the Shield. The social commentary in The Wire, coupled with the brilliantly developed characters, brilliant script etc
I wouldn't say that The Wire was more original.
And are you trying to tell me that McNulty wasn't as flawed as the characters you described on The Shield?
TBH if I wanted social commentary, I'd watch a documentary. It's the reason I hate reality TV - I don't watch TV for "real" situations. I watch TV to see how well writers can create a fictional scenario that makes me care.
The Wire isn't a bad show - not at all.
But neither is The Shield. They're both good.
But Fawlty Towers eats them both for breakfast, anyway, so it's all academic.