I manage a network like you describe: Two BGP edge routers, both routers accept a full eBGP feed from transit, both share routing information via iBGP. Both edge routers in my network have a complete view. If one transit provider is down or there is an upstream peering change, both still have a complete view. The only time they wouldn't have a complete view is during convergence or when there is a simultaneous outage of both transit providers at different physical facilities.I would argue that one can generally safely add information to his or her router's RIB (such as adding a local preference, weight, or advertising with prepends to direct traffic toward a better performing, less utilized, or lower cost peer), but that removing information from a router's RIB always comes at some cost (and some may find this cost perfectly acceptable).One needs to remember that removing information from RIB is how BGP works. If you have the common setup of two BGP edge routers, each with a directly connected transit provider link, the routers will only tell the other one about the routes it actually uses. Neither router has a complete view.
I could certainly use a default route (configured statically or received via BGP) instead, but that reduces my network's ability to make informed decisions. When one of my upstream transit providers is performing maintenance and loses a peer, I want that to be reflected in my routing so that traffic can be directed via the shortest path. When my transit provider's edge router loses upstream connectivity, but maintains connectivity to my equipment, I want that reflected in my routing so that traffic doesn't go towards the path that leads to the bit bucket. I can't detect those conditions and route around them if my router only has a default route.
