There are 2 things that make me put nothing but Sadowsky strings on my basses. The first is that they tone is consistant from string to string. When I hit notes on the low B string on some sets, it doesn't sound the same, the tone is very different. With the Sadowsky strings, they sound fairly even up and down.
Secondly, I got a pair of flats from them a couple of years ago, and the tone didn't sound very good, and one of the strings sounded different from the rest. After an email to them to ask about this, they just shipped me a new set the next day with no hassle.
Their customer service has always been great when asking questions, and when I add that in with the quality of the product, I see no reason to give my money to anyone else.