I know 7 people who have been playing Classical Guitar for over 40 years and have owned more than 10 guitars.. I tried my very best to extract the truth about this topic that has been bothering me for quite some time.
A few things to note before we get started :
1. There are many types of spruce - alpine spruce, German spruce, Italian spruce etc. And similarly, there are various types of cedar - for example western red cedar, Canadian cedar, American cedar etc.
2. A Guitar tops even grain and other symmetrical intricacies will reveal the woods real age, consult with a wood expert.
3. Not all spruce tops or cedar tops are equally good. Guitar with a higher price tag will usually have a better seasoned wood.
4. Besides cedar there is another similar type wood which is called Red Sinker wood, ( From Sinker logs which are found in the ocean ) it might cost three times more than normal cedar tops but the price is worth it.
Anyways here's the thing,
Most of these people said things on similar lines "The truth is, it doesn't make a big of a deal, both spruce and cedar wood have been used to make excellent guitars, what really mattered the most is the luthier's craftsmanship, bracing, finish etc" While some cedar tops were not as good as spruce but some were definitely better than the spruce is what some people had to say. Some even said "Go ask a luthier." Most lutheirs said the same thing "You cannot make a bad cedar wood sound great or a bad spruce one sound great, whether it's spruce or cedar, the wood has to be good and seasoned" But they did nod to the idea that "Spruce Guitars require more time to mature and open up".
Another fallacy which is currently being sold is that "cedar doesn't evolve, but spruce does " . To tell u the truth, both cedar and spruce evolves, and cedar evolves faster. However cedar doesn't have much to grow into. And some cedar tops sound open and ready at the shop. Then again, I'd mention that all acoustic instruments which are well built with the finest materials and if played and maintained properly will eventually sound more mature & rich and grows with age.
If a guitar with 10 year old Canadian Cedar top takes 2 years to reach 'x' amount of quality, then it would take a Guitar with 10 year old european spruce top around 3-4 years to reach that 'x' amount of quality. However after some point roughly after 5 years the cedar will stop evolving. But the Spruce goes on evolving. So if u get a spruce top & a cedar top today, play both equally for 5 years, and let me know how good your spruce top gets after 5-8 years.
Please note that for the example given above, you must have two identical guitars i.e. those that have identical bracing & binding patterns etc. For example if you want to experiment then consider having two Contrearas C4 guitar one is spruce top and one in cedar top.
Quick Facts : Spruce Tops generally are more trebly, they sound more punchy and bright, for some people they are too bright. It is generally said that Spruce top guitars are somewhat louder & versatile in nature and is ideal for a variety of music to be played on it. The individual notes when played contrapuntally sound more separated in case of spruce tops. They have a wider tone palette with more tonal complexity.
Cedar Tops have a soft attack, and are sensitive. The have a 'warm' mysterious tone. Does not have a wide tone palette, not tonally complex.
Famous Concert Guitarists who have used spruce : Julian Bream
Famous Concert Guitarists who have used cedar : Andres Segovia, Alirio Diaz.
It is generally said that Spruce top guitars are somewhat louder & versatile in nature and is ideal for a variety of music to be played on it. The individual notes when played contrapuntally sound more separated in case of spruce tops.
The Best thing that you can do is to get both done exactly the same way by the same luthier. Spruce tops are great for Baroque, Renaissance, lute pieces, Bossa Nova etc. for Romanticism & for some Spanish music Cedar Top is recommended. But in the end some things are better left subjective.