At the moment I am torn between Reaper and Cubase. I have used both for years, but usually end up using Reaper more because of it modular approach, simple and capable routing, superior customization, compactness and speed.
However, Cubase has a lot of useful tools, particularly for the composing, recording and comping stages, that I like very much. Nevertheless in my experience I get cpu overload in Cubase when Reaper in a similar setup would run at only 25% of cpu usage.
I have tried to figure out why. Maybe it has to do with the real time audio? Reaper sometimes uses a lot of cpu too. For instance if you insert heavy plugins in the master channel or enable record from a track that goes through a lot of heavy plugins.
In Cubase it makes no difference if you move plugins from the master channel and route the through a final group track. Record enabling tracks makes no difference either. Maybe this could be because Cubase always uses these resources to stay ready and hence is always ready for recording etc. without changing cpu usage?
Others claim that Reaper has some sort of anticipation of plugin usage that minimizes cpu usage. Of course, this same anticipation would increase cpu usage as soon as you record enable tracks with live fx added supposed to go through real time audio.
If you wonder why. Real time audio can only use one core in the cpu. There is a great Youtube video explaining this. There was a link in this forum some time ago.