This is one I was tempted to phone my help-desk guys about to clarify, but I'll give it a shot on my own -- and could be completely wrong, of course.
If I understand correctly, there's no such thing as a "standard-sized" DNS ... some ISP's have huge ones, and some are quite small, limited to the most popular (in the sense of frequently visited) addresses, like for Yahoo and MS.
Regardless of how big or small it is, if the address you're looking for isn't listed with your ISP's DNS, it has to pass the request on to an "outside" DNS server, possibly more than one in sequence, till the address is found.
I think Technical's right, for any given ISP you don't have any choice about who or what they use for IP lookup. But there's another thing you could try. Somewhere "out there" there's a utility that'll give you the IP for a given URL, and vice-versa ... if you make a note of the IP's for specific (but not "popular") sites you hit regularly, add them to your Hosts file, or even just make a small txt file so you can look them up yourself. Then put the IP rather than the URL in the address bar (or make it a favorite in IP format).
Usually but not always, that'll be faster than using a URL since it in effects bypasses the DNS lookp. But my ISP says it's no guarantee, because sometimes there'll be a "reverse lookup" to ensure it's a valid address.
