They are very much the same - the difference is the context in which you might say one more than the other:
a. I know some good pubs around here.
Say two male friends are taking a walk. One comments that this particular area might be a nice place to live. The other agrees, and adds that "I know some good pubs around here', meaning yes, I know the area well and a further desirable feature/attraction of the area is that it has some good pubs!
b. I know several good pubs around here?
HE: Can you suggest a pub that does a good counter lunch?
SHE: Well, I know several good pubs around here (that you could choose from).