it depends on the number of crewmembers....
if I was a Captain of a large starship with a full crew....then probably a Sovereign Class Federation starship. You can go anywhere at anytime and won't catch grief from anyone with a brain cell. Explore new worlds...dominate in combat....the Sov. Class can do it all.
If I could pick my 10 best friends and explore the galaxy, I'd take the Defiant
. We can cloak, we can fight, we can get in and out of systems as quick as any other ship out there. The Defiant
is essentially a Starfleet version of a BoP on steroids.