Checking whether a table has modified rows
Is one design pattern better than another?


Every code statement is a potential defect. If you can express yourself in a shorter form without sacrificing readability, then by all means you should. The less code, the less to read and debug, the fewer suspicious elements.


  Is there a performance difference in the two?


I don't actually know VB, but this is a common pattern in many languages, and it's clear that the performance should be the same, or the second might be even faster, thanks to some optimization magic by the compiler.


  Would my version with the using syntax have any unanticipated results?


Increased understanding among readers? You changed not just the writing style, but you also gave the variables more meaningful names. It's intuitive and a lot easier to read than the first one. Both seem to accomplish exactly the same thing.


  Should I leave the old code alone?


Probably. Don't fix what ain't broken. Although the original method is not implemented pretty, from the outside it doesn't really matter: it has a good name, and it does exactly what the name says and nothing else, it works. It's nice to make it nicer, but there isn't really a need. Now that you looked at it closely and know that it works, try to treat it as a black box, and remember not to open again. Use your energy for more creative tasks.