LMS and NCS will be merged in the next release, most likely in the coming few months. So the "LMS VS NCS" issue will be moot.
"LMS Vs other monitoring tools" is a huge question. It really depends on what you have in your infrastructure and what you want to do with your network management system.
If you're multi-vendor, LMS falls short as it is 98% designed for all-Cisco systems. On the other hand, few (or no) competitors offer the breadth of solution for a Cisco LAN infrastructure that LMS does. Also, LMS will of course have access to internal development resources and systems that no other vendor will ever offer. If LMS has a bug or IOS has a bug, it's one vendor who needs to fix it - no finger-pointing.
Many people use Solarwinds, for example. To begin to approach LMS, one would need both Solarwinds NPM and NCM. Even then you would not have the topology service or workflow that LMS gives you. You would also not have CiscoView. Likewise HP OpenView NNM falls short. As does What's Up Gold. They all do their intended function well - they just don't have the breadth of services built-in for a Cisco shop.
If all you need is configuration file management / archiving, then sure stand up an open source RANCID installation. It might be a bit cruder and require more Linux admin skills but it's perfectly functional. You won't get any support and that's all it does, but it does it in a workable fashion.
If all you need is performance management, use Cacti.
If all you need is fault management, use Nagios.
If you need fault and performance and are multi-vendor, use NPM.
If you need it all wrapped together and are a Cisco shop, use LMS.
