When it comes to bass I would 9 out the 10 times prefer a (sample of a) real bass guitar over a synth or virtual instrument. The main reason is that I think that it’s hard to find good sounding virtual bass instruments. The only one that I really like is Trilian. There is a wide variety of bass sounds to choose from in there and some of them come pretty close to the real thing. My favorite bass sounds in there are the old school electric bass guitar sounds. There are also a bunch of synth bass sounds in there that are pretty cool.
I love Kontakt! Native Instruments really did a great job creating this beast. I love it how they made so many different instruments for it and also got other manufacturers building libraries for it. There are new libraries for it coming out all the time. I really like the Vintage Organs from NI but also the orchestral stuff Project Sam made for it I use a lot.
Omnisphere I really like for it’s choirs and pad sounds.
When I’m using soft synths I always use Nexus. Especially for EDM type of sounds Nexus is great. Sometimes I like to layer different Nexus sounds to create one huge synth sound. Especially with chords and lead synths I like to use this technique. I compress, filter and EQ each layer separately and use S1 Imager to give each layer it’s own place. By doing this I can make the synth sound really wide and big.
A lesser known virtual instrument I like is Olga by Stillwell Audio. It’s actually one synth bass kinda sound that you can tweak with knobs within the plugin. You can set the LFO, saturation etc and create your own presets.