I have not found a good link for "Sonar vs Reaper" in recording functionality. So here is my own comparison:
First of all Reaper has ALL possibilities for recording which Sonar had (including AUX tracks), and it has much more features in that area.
At first look, Sonar and Reaper both have "Input", "Record Arm", "Monitoring" and "Record" buttons. But the philosophy is different and that can confuse at the beginning.
* Input for recording:
- Sonar can record input, audio or MIDI (on respective tracks). "Input quantize" for MIDI is the only processing allowed. Sonar can record Audio (only) output using AUX tracks.
- Reaper can record input, audio or MIDI (on any track). It has "Input FX" chain, which can process the signal before it is recorded (f.e. for MIDI that can be quantize, arpeggiate, velocity or any other MIDI manipulation, even conversion to audio with softsynth). Reaper can also record the output, so function as AUX track in Sonar. Note that it can record not only some other track output (as AUX in sonar), but also just own output. F.e. Instrument track (in Sonar terminology) can record own audio output (but not in parallel with live MIDI, so to record MIDI and softsynth audio output from live performance in parallel, 2 tracks are still required).
* Arming:
- In Sonar track should be armed explicitly.
- In Reaper in addition to explicit arming there is "Automatic arming" on selection. Note that you can select many tracks and all of them will be armed (in case they are in that mode). You can switch selection on the fly, also during recording.
* Monitoring
- Sonar has explicit "Input echo", independent from recording. For MIDI, Sonar has "automatic" echo based on focus (so for one focused track).
- Reaper has no explicit "Input echo". But it has "Record monitor". In practice, that is "Input echo" which only works when the track is armed. Note that "automatic" monitor has nothing to do with the focus (it is for auto-punch recording). In most cases, when you have an intention to record your performance, such binding to record arm state make a lot of sense (together with automatic arming). For the case when you need "Input echo" but you do not want record the track (so you want record something else while this track just echo), there is an option "Record: disable". When set, Record arm does not work as such but allows "Record monitor" to work (the discussion how good is that is ongoing since 10 years, find the thread on Reaper forum. From that thread you can understand the intention).