[b]It comes down to your satisfaction[/b]
I played the cave for a few hours since discovering it's existence on an IGN article. At the time I was at level 23 without having any purple items. I was in no "rush" to level up but I was investing a lot of time to find my first purple engram and hope that it wasn't a blue dud.
Before I found out about the cave, I had an enemy drop a purple engram for the first time. I was excited and anxious to get to the cryptarch to have it decoded. But as it turned out, it was a blue item lower than what I already had equipped.
The cave was a way for me to find that first purple item. Throughout the 3 hours I spent there I didn't find ANY purple engrams. Even leveling up the cryptarch and receiving the "special gift" resulted in blues.
Today I received my first purple item that I EARNED from the Queens Wrath. I am glad that the first purple item I have was obtained this way, as it will be the item I will remember the most. A purple item from the cave would not have given me that feeling.
In the end, I feel more satisfied with earning my purple items through working at them (knowing that they will be handed out at the end of a hard fought battle) instead of hoping that it drops from a low level cave dweller, a strike mission or an end of mission roll.
I will move on now to find my first exotic item using the available avenues in which to do so.