Full BGP Routes versus Default route - Multihoming with Two Edge Routers

Why would one want to receive full BGP routes instead of default route?

I'm setting up a second edge router for internet redundancy only using BGP in a multi-homing to two different ISPs. I'm noticing that the current primary is receive full BGP routes, and the secondary too (the configuration was there) but now setting up backup ISP connection now.  Both edge routers have enough memory to receive the full routes but just thinking since I'm implementing the standby router, I can just receive default route on both routers? or even just on the standby if we want to just leave the primary edge router intact?  Just thinking now might be a good time to change if that will simplify things.  

I can see that if it was multihoming to two different ISPs on the same router, it may make sense to receive full routes such that if a route disappears from ISP-1, then the standby router might be used when that happens.

But in this scenario that I'm working, it is purely a active\standby scenario.

Thank you!