SSO is always better then RPR+ if you IOS supports the same because the switchover time with SSO is less then 3 seconds where in RPR+ it is approx 30 seconds.
SSO needs minimum 12.2(18)SXD and as you mentioned you have 12.218 release I will recommed you to opt for NSF with SSO.
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SRM is the good option rather than RPR+ as RPR+ gives you the switchover arnd 30-60 seconds while SSO gives you subsecond failover with 0-3 seconds.
Starting with IOS 12.2.18 code we default to SSO. RPR+ was used prior to the 12.2.18 Code. Use SSO/NSF for L2/L3 HA. Prior to 12.2.18 code we were supporting SSO/SRM
HTH,Please rate if it does.
How does SSO/NSF work with MPLS LDP, I am testing and have an MPLS network I do not get 0 - 3 seconds repair time, it is about ~30 Sec same as RPR+