still depends if you will use full table, and how the vrf-s.
"..For full BGP routes, you should consider a router that can take at least 256MB of RAM. I am working with a pair of 7206VXRs (NPE-G1) to separate ISPs, and each router is using around 161MB of the installed memory (1GB). At least 100MB of that 161MB is tied up by BGP..."
"the 3845 is higher thruput than 720x / NPE-400.
the interfaces are a bit cheaper on the 3845 as well.
also — last time i checked the 3845 was the smallest / cheapest box that can
take dual power supplies."