I agree it's hard to compare grand tours from year to year, since they change substantially. This was my first year watching the Vuelta, also. As a GC race, the Vuelta was probably better this year, though neither really ever felt in doubt. The much shorter stages with intense mountain finishes made for very exciting races (Vuelta). And the higher percentage of mountain stages made it much more about the GC guys. Against that is the fact that most of the best GC riders were peaking for the TdF, and the prestige differential definitely makes the Vuelta feel like the lesser race. OTOH, the sense of desperation (to salvage a disappointing season) in the Vuelta makes for some Quixotic attacks and more surprises potentially.
The TdF has the edge on varied stages. It seems like a wider variety of rider types have a chance at stage glory there. The downside to that is that some TdF stages are staggeringly long and boring, and it's just a game of survival, with some minor riders doing TV break-aways until they're inevitably reeled in for a tired bunch sprint.
The TdF also has the edge in the points competition. When Sagan isn't DQ'd, his style of racing brings a fun dimension to the TdF. Even with him gone, you have the cream of the sprint crop in there trying to nab stages and glory.
It's great that all the GTs have such different flavors.