OSPF vs ISIS in MPLS ?

• Some routers, called L1/L2 routers, belong to both area types.
• Unlike OSPF, IS-IS routers are not required to be connected to a contiguous backbone area. In fact, the backbone area can also be segmented in IS-IS.
• IS-IS uses the concepts of router levels, which is similar to OSPF areas. L2 routers are similar to OSPF backbone routers, and L1/L2 routers are analogous to OSPF ABRs.
• With IS-IS, there is no restriction that all backbone routers (level 2 routers) be contiguoussuch as the backbone area of OSPF. 
• In OSPF all areas must be directly linked to area 0, and the backbone area must also not be segmented. 
• With IS-IS, the backbone area can be more easily extended since all L2 routers need not be linked directly together.
• With regard to CPU use and the processing of routing updates, IS-IS is more efficientthan OSPF. 
• In IS-IS, one LSP is sent per IS-IS router in each area (including redistributed prefixes [routes]), compared to the many OSPF LSAs that would be sent. 
• Not only are there fewer LSPs to process, but the mechanism by which IS-IS installs and withdrawsprefixes is less processor intensive. 
• In IS-IS, the entire SPF table is not refreshed periodically like OSPF, which does so every 30 minutes by default.

IS-IS

With ISIS it is easier to extend then OSPF. ISIS can run both IPv4 and IPv6 without doing that much changes. On the other side to run IPv6 you have to use OSPFv3.

OSPF is a Pain to implement. You can hardly use any neat internal implementation tricks. Because everything is overspecifcied in the specs. 

So I prefer IS-IS

OSPF  in my opinion is better for mpls networks

Most MPLS networks nowadays work with IS-IS

IS-IS is better than OSPF for MPLS

--IS-IS --> is easier to implement

--OSPF --> is more efficient

IS-IS is more flexible with mpls