L2/L3 design question

Hi there

I've been doing some RH for a few companies lately. One company has their setup like this:

Cisco NCS <--> QFX5100 Juniper aggregators <--> 4948E TOR.

They run iBGP between levels to pass the TOR routes upstream and somehow use IS-IS too, I think to advertise loopbacks IP's.

I was talking to a couple of network engineers I know and they said "no no no no no", route all your VLANs on your edge routers in a set up like that (re: cisco NCS, or in my hypothetical chat with them, Juniper MX), and pass the vlans down to the QFX level, and then pass those down to the TOR. The gist is, route on the router, nowhere else.

Is there a reason either one of those ideas is bad?

Signed,

guy that loves networking and wants to learn