If you need more info, it is important to understand the history. Over 10 years ago computer software was replacing hardware samplers. Cake, along with SONAR, developed another soft synth player environment called P5. P5 V2 was coming out and they jumped on the computer sample bandwagon. So they hired REné Ceballos who had already developed several synths, including Z3ta. He also had SFZ as a replacement for Sound Blaster Sound Fonts, at that point an almost universal format and developed a Sound Font player, which you can still find for free, I believe. Anyway, for P5 he developed Dimension, a sample-playback synth that not only had a good faceplate for editing but one you could use further SFZ editing with to expand your palate. Unfortunately, SFZ is still today a script controller, using word pad etc.
Dimension only came w/ P5, so they used the same synth but added more samples/programs and came up with Dimension Pro as a separate product. René took the same synth, added step sequencers to the LFO etc controls and different samples and voilá, you have Rapture Pro. Both those synths got packaged w/ SONAR and they have combined the 6 elements and step sequencers of Rapt w/ Dimension's larger, acoustic library and voilá, you have Rapt Pro (along with more programs/samples and other enhancements).
The same sfz synth engine powers all of them, and they have the same faceplates and operating system, so there is no learning curve. For a good price (or it was) you combine both synth libraries under one engine and get more of libraries to boot. And there is nothing now to stop you from easily adding step sequencers to your trombone samples and other out there editing.
It is a nice and simple 10-year progression of what is essential the same synth. If I was starting out today I wouldn't load Rapt - I already haven't downloaded DimPro.