Cedar is slightly softer and less stiff than spruce and this can result in subtle tonal differences as mentioned by several people. It is only one of a number of important factors, however, and body wood (e.g. rosewood, mahogany, maple or other), bracing pattern, general build quality and tolerances, nut and saddle materials, type and gauge of strings, etc. will all contribute as well. Cedar does change a little with ageing but not so much as spruce. Swiss pine is another fine tone wood, again with subtly different properties.

There is no "better"... it will really depend on the sound that you like. I have owned instruments with spruce (Englemann and Sitka), Swiss pine and cedar tops and most have been fine in their own ways. Currently, my two main guitars (electro-classical and "000"-sized steel string) are cedar topped and all of my mandolin family instruments are spruce-topped.

For these reasons, as others have said also, it is always better, where possible, to really try the instrument out before buying.

RS
(ex-instrument repairman)