If lots of your training is already in PPT, then maybe Articulate is a good be: Import your PPT, add some audio and a couple questions and after export, you are good to go.
It uses PPT as the basic development platform and plugs in over the top. Your training looks like a glorified PPT.
Captivate is great for capturing mouse movements and screen shots. If you are developing training on a new computer system or software Captivate is really, really good.
Not suitable for more advance e-learning.
Lectora is great for everything. Everything Articulate and Captivate does, you can do it in Lectora. Plus, the flexibility of Lectora allows you to go beyond and really do some creative eLearning. If you want to build training distributed over the web, and you have a team of creative designers who want no limits, try Lectora.
Not as intuitive. There is a learning curve.