Hi @EWSG
Welcome to the forim.
It all depends on what you are trying to do, and your level of knowledge or experience.
I have InstaComposer 2 and, quite frankly, am not overly impressed by it, but I do use it occasionally. There is no midi import so if you generate a harmonic sequence in Scaler 2 then you will have to manually enter it into InstaComposer 2.
It does have the advantage of generating bass and melodic sequences from a harmonic pattern but in my experience the algorithms used tend towards electronic music (not necessarily a bad thing, just a limitation).
If you decide to swap the workflow around and generate a song in InstaComposer 2 then drag the midi from the verse, or harmony into Scaler, then you can use Scaler to generate substitute chords for those originally generated in InstaComposer 2. This can be interesting as you can then create a second scene in InstaComposer 2 with the new harmony and then generate a new bass line, melody etc. As InstaComposer 2 supports 8 scenes each of which may be up to 32 bars long this does raise some creative possibilities.
I have no experience of Melody Sauce although again I think it may be oriented towards EDM.
My preferred tool for generating melodies and bass lines is ChordPotion, but again this takes some effort to learn as it is not intuitive (the pattern editor is different) but does have many good features that have to be discovered.
For an introduction to using Scaler’s in-built melodic phrases try Introduction to Using Playback Performances to Give Interesting Melodies.
There are many tutorial videos on YouTube on the School of Synthesis channel.
There is also a very good online Scaler Course from The School of Synthesis.
Finally, I believe that Scaler 3 may be released later this year and and I am hoping that it will include some further developments on the melodic side. Certainly there have been suggestions in that area.
Hope this helps