From the seat of the pants feel, the 2X on the 300 feels pretty quick on both bodies, but I would give the edge to the 5d3. Probably since the 300 is a 2.8 to begin with, there is more light to work with compared to the 2X on the 500 so it would make sense to be faster.
I doubled down this morning at my camera shop and paid for the 7d2 in advance which bumped me to the front of the line, for whatever that is worth. They are selling it at the same price as B&H etc, so the advantage is that I am in the local market versus the national.
I meant to process yesterday's shots for comparison, but then I went out and shot more today, and then also stopped in Yountville on the way home (Napa wine country), so I am pretty much done for the night
