First... take a look at that juicy hoppy goodness:
As you can see... they pretty much look identical in color, clarity, and head. I didn't use any filters on that picture to try to show the color of the beer as true as possible. Upon a really close up to the light inspection the 2/15/16 batch (on the right) is very very slightly lighter. You'd never be able to pick that up by memory unless you have some sort of photographic memory, because even side by side it's damn near impossible to differentiate. It also might look like the volumes were off, but it turns out the glasses from the last two Grand Reserve days aren't identical, so rest assured, they were both full bottles.
On to the aroma... I started to notice a difference here, with the newer batch having more of a dank funky piney aroma and the older batch being strong with tropical fruits and the dankness in the background. Don't get me wrong, there is a LOT of overlap in the flavors coming through, but each seemed to have a different flavor come through the strongest.
On to the taste... the older batch (1/13) was still very tropical up front, but there was more dankness coming through than on the nose. The lingering flavor on the tongue at the end was more piney than fruity, but all the hop flavors mesh so damn well. The newer (2/15) batch was still more dank than the newer batch, but there were some tropical notes coming through before it faded to the resinous follow-through.
As I kept going through the tasting (rinsing with water between batches) I couldn't make up my mind which I preferred, but there were definitely slight differences. My wife actually preferred the older batch, but that's likely due to the tropical fruit dominance. I would probably take the newer batch, but I like piney resinous IPAs. These are brewed the same way with the same water treatment, same malts, same mash schedule, same hop schedule, so I attribute 99% of the variance in flavor to the age difference.
One thing is for sure, whether it's 11 days old or 44 days old, Ghost In The Machine is fucking delicious.