Neither. Any time from the beginning of November through the end of October is the best time to buy parts. Yes, I said that right. All year long. Especially if you are looking to buy parts which are current, this year technology that has been released within the last twelve months.
BF and CM deals are usually ONLY on technology and components from the previous year or two, or older, that they are trying to deplete from their inventory and need to get gone in order to make room for other newer incoming or existing products. When you see a sale on a product that is priced in a way that seems reasonable to you, then THAT is the time to purchase it. As we've seen in the past, waiting on BF or CM deals often results in either not being able to get the hardware you want because it becomes out of stock everywhere and no more of it is coming because it is old tech, or the price goes up because stock gets low from so many people purchasing it.
I've found much better deals, in general at least, buying AFTER the holidays for current hardware so that the demand for it from seasonal shoppers goes back to normal and stores are able to refill their inventory with product from the manufacturer, or watching for sales throughout the year and buying when I know the price is good. Waiting for BF and CM has never resulted in anything other than a good deal on something old or no deal at all.
If you are looking for older hardware, then possibly you can find something worthwhile but it will be the ENTIRE period of November 1st through December ~20th, not any particular day.