Greetings, I will also lean to the second option, if you want to go even further, you can create a policy to have only your BGP routes as contributing routes for that generate route, and if those BGP routes are gone, you will stop advertizing that default route so you would not have your traffic blackholed or sent to another next hop if you don't have a route to the ISP
If this solves your problem, please mark this post as "Accepted Solution" so we can help others too \:)/
Lil DexxJNCIE-ENT#863, 3X JNCIP-[SP-ENT-DC], 4X JNCIA [cloud-DevOps-Junos-Design], Champions Ingenius, SSYB
If You receive 0/0 and ::/0 from Your ISP, You don't need to bother about generated routes.
Generally speaking, creating 0/0 generated route is more pain than it's worth because with incessant BGP route churn in the wider internet, JUNOS RPD is going to be constantly reevaluating contributors (something like 800K contributors!) and reselecting the best numerically lowest contributor to make this contributor' nexthop the generated route' nexthop.
Ditto for ::/0 generated route, albeit with lesser contributors but they are growing.
We are not running IBGP internally, so have rely to OSPF.
This is a MAJOR disadvantage because without iBGP, You can only run internet in GRT and LDP-based MPLS services such as LDP VPLS and L2circuits. And that's all.
All other services (L3VPN, L2VPN, EVPN, flowspec etc) use BGP so I'd say start planning for iBGP before Your network grows large.