For the student, Dominant by Thomastik with a silver D and a Goldbrokat E is an affordable and durable set. For those looking for more warmth and complexity the Infeld Red set is also an affordable choice.
For the accomplished player the above sets are often still popular. Obligato and Perpetual by Pirastro are high quality sets. Obligatos provide warmth and clarity and are often the choice for symphony players. Perpetual have great attack and depth with warmth and complexity often the choice for the soloist. Always use a silver D for violin. Paul also recommends Rondo by Thomastik. Rondos provide a quick bow response and can brighten the tone on an instrument. They work well for soloists and recording musicians. These sets get a bit more expensive!
E strings are temperamental. Fortunately, they are inexpensive enough that individuals can try several out to see which works best. E strings come in different gauges; the higher the gauge the brighter and harder the sound. Some E strings worth trying are Kaplan Golden Spiral, Hill, Jargar, Pirastro Silvery, Pirastro Gold, Pirastro Olive, and Pirastro Eudoxa.
For the student, again the Dominant set works well. However, with viola, the aluminum D string is preferred.
For the accomplished player, again the Obligato and Rondo sets are more expensive but worth trying. For a viola needing more punch in the lower end, a Tungsten Spirocore C can help. Other A strings to try are Larsen and Jargar.
Most cellists demand more bottom end sound with a great singing A string.
For the student, an affordable and durable set that provides quality sound would be Larsen for the A and D strings and Spirocore Larsen Tungsten G and C strings.
For the accomplished player, Versum and Rondo by Thomastik provide a warm, professional experience. Rondos continue to be a very powerful and bright sounding string. They compliment cellos with a more subdued bass sound. Versum and Versum Solo add a punch to the instrument that helps in orchestral or professional settings. As these sets are more expensive, Paul recommends trying both to find the set that fits best with your instrument and play style.