Virtual router routing instances enable us to isolate traffic without using multiple devices to segment your network.
Each virtual router routing instance consists of sets of –
•Interfaces that belong to these routing tables
•Routing protocol configurations
•Routing option configurations
Logical system is one step above Virtual Router and VRF concept of working. Logical systems work like full-fledged Routers i.e. their own Routing instances, own management independent of other other logical systems in same Router chassis. The benefit one gets is that in case one process in the Logical system or crash of daemon happens , it does not impact the process in other Logical systems. Furthermore ,with Logical system, one can allocate the quota of CPU cycles to be used for each LR. This type of indepth resource segmentation is not available with Virtual Router.
Note – Logical System was formerly called Logical Router until release 9.3 . Post release 9.3 it as called Logical System instead of Logical Router.
Related- Juniper Virtual Router vs VRF