Simple answer: use both! That is what I do, and many others also. You did NOT waste any money on Cubase. Even @RadioTal has mentioned he uses Reaper some times for the editing phase on some projects. From reading his posts, it’s clear he has a carefully delineated and separated production process, which is very organized:
There’s a lot you can take from his posts BTW, and he’s clearly knowledgeable IMO.
But the key statement in this whole thread might actually be from @Sunshy when he said:
I could not have said it better myself.
So, @TruTheaterRadio, you’ve come to a crossroads, and this thread, IMO, is an outstanding resource. Lots of good thoughts here, and in the end I think you’ve got a glimpse of a lot of the variables, and over time, you’ll develop and refine your own unique production process that will suit your projects and your workflow preferences, which will be different than other people.
Now IF you really do decide to buy Reaper too, here’s exactly what I suggest you use BOTH Reaper AND Cubase for in your production pipeline, to take advantage of the BEST features of both DAWs, to maximize your time and creativity.
My personal approach to all projects is to use the best tools on the market for the task at hand, and it turns out the combination of Cubase + Reaper is a killer audio drama combination. My suggestion is to explore how you can maximize both DAWs for your benefit. You’ll need to adjust your pipeline to keep project files organized of course, and you’ll need to differentiate the steps in the production process to some degree so that you don’t create a giant mess. If you’re willing to do that, then Cubase + Reaper will be an amazing duo for you.
First, keep in mind, that once you figure out your production process, it’s not hard to maintain projects and sub-elements of projects in both DAWs. Just stay consistent and organized. You also now have the DAWproject file exchange format which can also play a role in your process to some degree. It is indeed limited, but both Cubase and Reaper support DAWproject (in Reaper, it is a third party tool, but it works pretty well for simple project exchange.)
Do your editing in Reaper. As discussed, it’s that multi-track click-and-drag ripple editing which will save you time and reduce your fatigue as you refine the timing of all the dialog.
Do anything that needs a musical context in Cubase. Especially if you are scoring, but also useful if you are just adding music tracks/layers/etc., then Cubase in general will have more creative tools IMO. Reaper has many creative tools too, but Cubase is Cubase, it shines in this area.
Cubase excels at certain areas of sound design too. With Cubase’s modulators, Sample Tracks, DOP, and Padshop alone, you have a surprisingly powerful set of creative sound design tools appropriate for audio drama. Learn those features, and your projects will love you for it. People underestimate things like Padshop, for example, but it’s a wonderful little sound design synth, and you already own it! Drop your own sample in it, mangle it, and create a fascinating texture in the context of your audio drama. The other included stock plugins are also very good, and there are some gems in there. Use them.
Either Cubase OR Reaper can be the final DAW for your mixing and mastering stages. There are advantages to both, but it depends on your preferences and production process.
IF you want to have an organic, super flexible creative production process that will potentially include a lot more ripple editing later into the production process, then MIX the project in Reaper.
IF you want to have a more structured production process, with carefully delineated steps for each phase, and you don’t think you’ll need more ripple editing later in the process, then MIX in Cubase.
And if you need the additional tools that Rajiv points out, then eventually you’ll want to upgrade to Nuendo, and then use Nuendo + Reaper. 
For the mastering stage itself, you can achieve the basic appropriate levels, loudness, and compliance standards in any of the major DAWs today, but there are some very nice tools in Cubase and even a few more in Nuendo as has been pointed out by Rajiv. You may eventually want to invest in third-party plugins to assist you as well at some point. This is a huge topic by itself, but suffice it to say you will have plenty of tools to do it in Cubase/Nuendo, and Reaper.
Couple more thoughts about features to take advantage of in Reaper that I find useful in audio drama (and sound design, and post, etc., etc.)
1 - Learn to use Item/Take FX in Reaper. This is, in some ways, more powerful than DOP in Cubase/Nuendo.
2 - For complex plugin routing, learn FX Containers in Reaper. Cubase/Nuendo do NOT have a feature like this right now, and you’d need an FX chainer like DDMF or Blue Cat products to do something similar. FX Containers are a great tool, when needed. (You may never need them, but if you do, it’s there in Reaper already.)
3 - If you start to develop complex sound design elements OR just sections of repeatable audio chunks that you want to reuse or repeat in all the episodes of your audio drama, learn Subprojects in Reaper. Cubase/Nuendo also do NOT have a feature like this. It is a huge time-saver since you can nest entire Reaper projects within other Reaper projects, so this is ideal if you create your intro, sound design elements, or other sections of audio that are the same across all your episodic content, and you just simply put them into Subprojects and you can easily reuse them and then later edit them if you want to, and even have their contents replicate out into all the episodes. Learn this secret weapon of Reaper. Very few people understand how powerful it really is. I run into seasoned veterans who STILL don’t grasp how powerful subprojects can be. It’s a deceptively simple feature, but once you start using it, and understand the ramifications of how it nests inside other projects (which can then nest inside other projects, ad infinitum), it can streamline your productions and sound design process.
Lastly, I’ll just suggest that you have fun on your journey. The combination of Cubase (or Nuendo) + Reaper for audio drama is simply epic. The sky is the limit with what you can do, and by the time you hit your limits, you’ll know exactly what other tools you are missing, and you can easily add them to your toolbox.
Cheers and good luck!
