To be honest… (I’m always suspicious when people start a statement that way myself. so…)
To be honest, it really comes down to the interface, just like with hardware synths. Yes there are more options than I know what to do with, but some of those work really well, and some not so well. How easy is it to imagine a sound, or to have some idea about what one wants to accomplish sonically, and then to realize that sound.
Take Granular Synthesis just as an example. There are so many options, but Padshop stands out. Pigments is great, and Straylight/Pharlight is also good when targeting something more ambient because the presets. HALion is also a good option, especially when mixing styles like with Pigments. Reaktor has it’s place and is fun to play with from a cerebral perspective, but the interface is more useful for experimentation.
Massive is great for 90s style techno bass but is time consuming to get your head around, and the quality of what you can get from HALion along the same lines is just amazing. It comes down to the interface. Massive X is a vast improvement when thinking through sound design, but it has nothing on Pigments, which provides an easier to visualize interface.
So to the Honest part. It’s like looking for an app to do something on your phone, you get a few, usually the free version, and half of them have some messed up payment model, or want you to create an account, and of the rest one or two stick out as genuinely being useful. It’s the same. Maybe it’s a matter of preference, but it comes down to the interface more often than not.
Then it’s about performance and the tone you get.
When it comes to samplers it is really more to do with sampler platforms. There are two primary options. HALion and Kontakt. Almost everything has a Kontakt version, but the Kontakt interface is horrible, so HALion is preferred, but not always an option. The most frustrating thing to happen is when you buy the Kontakt library and they come out with a HALion version, but you would have to buy it all over again. The choice of library is more about how it sounds though.
Then there are the emulations. You used an instrument in hardware, and you know what sort of sound you can get from that hardware, and you want that sound, or that experience. The interface hopefully is going to be close to the original, so it’s more about how well it emulates the sound and what performance you get out of it.
Sometimes it is about what you know. If you know an instrument already, if you spent the time to learn it, then you go back to that instrument over and over. But again, that is sort of about it’s UI. I have a huge library of instruments I never ever use. Sad, but when I know how to get what I want from a small set, I just keep going back to them.
My take get Absolute! it’s a great place to start. If you are composing, then Kontakt is a must! Pigments may also be useful because it’s interface is intuitive. Not as structured as HALion with which you can get close to the same benefit from, but a great interface for experimenting. Nothing beats NDSP for Amp Sims, as far as sound quality goes. I regret all of my other amp sim purchases.
The number one argument against this diatribe is the sonic quality you want to achieve. After you have heard everything a lot you start to recognize the variations to presets that have been used. Think of it like this, every time you hear a Line6 amp sim, you know without any doubt that it is Line6. Your brain pattern matches something about that technology that makes it recognizable. Once you have heard it, you can’t unhear it. Two seconds in, and you know it’s Line6. Synths are the same way, you hear Absynth, and you just know. Sure it has a great interface (for it’s time), but it also has a district je ne sai quoi.
I did not personally have to spend a lot on most of my software that isn’t from Steinberg, so it isn’t fair for me to talk about exploring and finding the interface you synch with. But demo versions are still a thing, right?
If I had it to do over again, I would buy Absolute and learn HALion, take a class in synthesis or watch a full tutorial class on it. I would learn synthesis and experiment with Pigments. I would have to have Kontakt. There isn’t any way around Kontakt unfortunately. But never buy anything for Kontakt you can get in HALion.
As to layering and selecting samples, it’s the same as improvisation in note selection. It’s similar to composing. Look for a sample that is similar, to what you hear in your mind, hear it. Play it in your head first. Then go for the kind of sample that makes sense. Try to know what you are going for. Once you have something close, then jam, let yourself go, you can always refine the tone from the performance later.