A a recent convert to proper expensive samplers - Spitfire Audio, I'm a convert but the two of us who do our music projects are quite different - I am a generalist. I don't play anything exceptionally well, but I play to a standard high enough people pay me! My friend and long-term colleague and collaborator is a proper pianist - of the play at least 4 hours a day for practice type pianist. Excellent sight reading, very good ear and all round good guy. He struggles with technology but I'm pretty good with it so as a working pair we're good.
The need to have realistic orchestral sounds for an on the go project meant we both bought the Spitfire product and a few others too - and swap files easily. However, to produce an accurate rendition in the machine of real strings, woodwind and brass means pressing a key is not enough - you also need modulation, expression volume, vibrato, and critically, keyswitch changes to match the note you play - so if you are playing fast, loud, staccato notes, this needs a fast, short sample, yet the next sustained note needs a different type of sample - so you need to play with your right hand the notes, and then your left hand is changing the sounds, bringing each note in and out and you have to play it! Watch the Spitfire Audio videos to see how they do it and you will get the picture. I've become competent, but not yet fluent, but my friends hasn't - so at the moment, he's playing, and I'm then adding the other hands - he just cannot get the hang of it. Part of the problem is that real string, brass and woodwind instruments are not played with keys - they're done with bows and lips, and teeth and tongue - and on a violin, for example, you never go from silence to full volume instantly - every note ramps up to the required volume - quickly or slowly, and once it's sounding, it might increase, or get quieter.
I ended up buying a proper master keyboard that has programmable faders so I can control all the things available - even so, sometimes a very simple little melody takes umpteen plays to get right. If you just want ensemble strings, then at the very least you need control of volume (midi controller 7, or perhaps 11, expression) but modulation is also slightly different on some samples. With something even as basic as Halion on Cubase - controllers can make string sections sound more realistic.
Not wishing to confuse it even further, but you also need to consider the notes you select. Close together block chords rarely sound authentic - in practice - you might have a couple up top, one a bit lower, another lower than that and then one very low - absolutely two handed chords, leaving no limbs left!
