I have recently been thinking about how, in the classical and romantic eras at least, instrumental music is divided into symphonic music and chamber works. The former are more popular, not because they are of higher quality, but because they are more accessible. Despite being larger in scale, the orchestral sound immediately imposes itself upon the listener. I personally prefer chamber music, whether it be solo piano, string quartet or something else, for a number of reasons. Firstly I think that the best composers through the classical and romantic periods actually wrote better chamber works than they did symphonies, this is partly due to the fact that in chamber music the composer cannot disguise a lack of musical interest with orchestral effects. This brings me to my second point, which is that more often that not composers overlook weaknesses that arise like fissure in the large scale form of a symphony, choosing instead to fill these gaps with surface aesthetics. This is particularly the case in a composer like Schumann, who wrote incredible chambers works and lieder, the violin sonata in A minor and Dichterliebe spring to mind, but whose symphonies were simply not cohesive.
I have recently rediscovered romantic music, which I previously believed to be a worthless era through the chamber works of Schumann and Brahms. Chamber works are more difficult firstly because it is easy enough to simply get a snapshot of a composer by downloading the complete symphonies, rather than delving into the murkier depths of the always innumerable small scale works of any well known composer. I recommend that keen listeners take the time to research a composer and get an idea of what they contributed to the string quartet, piano and chamber repertoire rather than simply download the complete symphonies.