There are several types of DNSBLs: geographical,
by provider, by type and 'know sources of spam'.
The geographical, provider and type based are your choice to
use or not to use.
The 'know sources of spam' are somehow a 'political' thing:
some DNSBLs list more agressiv while others have a more relaxed
listing style. The first one means that occasional you might
find an entire large provider listed as source of Spam due to
misuse by one of their users (until the provider acts and removes
the problem, what can need several days).
Advantage is an 'automated' maintenance by the DNSBL operator.
The speed can depend on cache handling. Caching more IPs will
speed up processing, using the progressiv cache will give it
an additional boost. But it will raise false positives/false