Over the forty some years I’ve been a guitarist I’ve played and owned a ton of instruments ranging from plywood topped to hand crafted guitars. I’ve fallen in and out of love with many different types of guitars, and yes, there are many which I will always regret parting ways with. I must say, however, that when in the hands of a trained performer, nothing really compares with a quality acoustic nylon string in terms of tonal palette or as a vehicle for sensitivity and expression.
The trained performer/player is an important caveat when it comes to classical guitars, because so many different things impact tone production on the instrument. Steel string guitars are much more forgiving when it comes to tone production, regardless of whether you play with a pick or fingerstyle. The type of pick and the angle of attack do make a difference, but obtaining good tone on a steel string is a much simpler problem to solve. Likewise, when playing fingerstyle the angle of attack and having a decent nail surface has an impact, but when it comes to a nylon strung instrument the need for attention to detail is elevated significantly. Nail care becomes a serious need, often involving multiple files and ultrafine grit sand paper for finishing the process. The shape and smoothness of the nail edges make a huge difference in tone production, as well as angle of attack and where the string is plucked. Different finger stroke techniques also come into play and have a much more pronounced tonal shift than when done on a steel string.
The tactile experience of playing a classical guitar is quite different from most steel strings, and is one that I find to quite pleasing. The strings themselves are much more pliable than steel which effects both the tone and the responsiveness to manipulations like pull-offs and hammer-ons. I find them to be less fatiguing to work with as well due to their softer feel. Classical guitars tend to run smaller in body size than most steel strings, although there has been a shift here due to steel string builders producing a wider array of body sizes over the past 30 years or so. Classicals also have wider and much flatter fingerboards, often not having any radius. The standard classical guitar fingerboard is 2” (52mm) wide at the nut with a 650mm (25.5”) scale. The scale length is pretty much the same as most steel strings, but the width is significantly wider which allows much more independent movement for both the fretting fingers as well as the plucking fingers. I find this to provide an optimum ergonomic situation for most of the music I am interested in working on, particularly when dealing with multiple voices working through the pieces.
Classical/nylon string guitars do have some drawbacks. For one thing, due to the nature of the instrument and the strings themselves, they are more quickly affected by shifts in heat and humidity, which affects the stability of the tuning. The strings also stretch much more than steel strings, which requires time to establish stability. Generally speaking, changing steel strings on the same day as a performance is not a big issue, and breaking a string is a quick fix. Nylon strings both take more time to install on the instrument, as well as to stabilize. This necessitates a playing in period, so a broken string during a performance is going to have an effect on the rest of the evening. However, most of this can be dealt with through planning ahead and staying on top of regular maintenance. If you wait until the strings break on a classical to change the strings, your tone will already be suffering more than doing so on a steel string anyway.
All in all, while steel strings and nylon are technically the same instruments, guitars, they do tend to frequently serve different musical purposes and are in many ways different animals. One would certainly hesitate to use a concert classical to play in a bluegrass ensemble, for instance, because the instrument was never designed to perform that purpose whereas a steel string dreadnought specifically does suit that job. However, from my perspective the concert classical has it hands down over the dreadnought when it comes to range of tonal color and sensitivity any day.