Where you already have some Chef recipes to build your application boxes and are happy to run directly on VMs, OpsWorks really shines. It won't do anything too complex for you, so it only really works well for simple stacks (load balancers, application layers, database layers). If you want to do more complex infrastructure, Cloudformation or Terraform are probably worth looking at.
IBM Rational ClearCase might be better suited for a smaller / simpler code base. Larger code bases really slow it down... but then again there are better alternatives out there for source control
Rational ClearCase is excellent for handling versioning and branching. No other tool I've used has the depth that ClearCase has when it comes to handling complex branching scenarios and identifying where certain versions of particular files are within a particular configuration.
Rational ClearCase handles parallel development of many dependent applications really well.
The use of ClearCase Views to switch between projects and configurations is extremely convenient as opposed to the local workstation model of the competitors.
Getting up and running with OpsWorks is a very technical and potentially time-consuming process. You need to know the ins and outs of Chef/Puppet if you really want to get into it and there isn't a convenient way to test out the environment locally so debugging can be time-consuming.
To take advantage of some of the newer AWS instance types you need to be running on a VPC, which again is a pain if you don't have a DevOps team.
The error logs and monitoring metrics in OpsWorks are pretty basic and haven't changed much over the years.
Unless you pay for a pricey support package getting support on OpsWorks will be pretty slow. Documentation is also relatively limited and sometimes hard to follow when compared to competitors. Generally, we've been able to get the answers we need from OpsWorks support when we run into problems but don't expect rapid responses.
OpsWorks isn't really a direct competitor to Terraform/Cloudformation, but it does allow you to do some of the more simple things on offer quite quickly and effectively. Opsworks was used for this reason, along with existing internal knowledge of Chef. Along with some of the other services on offer from AWS, it is good to use as a stepping stone along the way when building your systems - or perhaps it would be entirely suitable for a fairly simple project.
If development is centrallized to one location and your company releases hundreds of customized versions of your software per year, then ClearCase is the best tool for managing the complexity of multiple versions of customized software. If your company has globally distributed development, then I'd recommend Team Foundation Server over ClearCase. If your organization uses Agile Methodologies, then I'd recommend TFS with GIT.
