Little else in the casino is more horrific than this bet, it's the equivalent of plunking two slot machines down in front of a slots fan, one with an atrocious payout rate but fancy graphics and sound, and the other with a half decent payout rate but no bells and whistles.
What do I mean? I mean the big 6 bet is the fancy looking slot machine, and the place bet for 6 is the unglamorous one. The fact of the matter is the place bet on a six or eight is exactly the same thing as the big 6 (or 8), the only difference is what you get paid. For a place bet on the 6 or 8 you get paid 7 to 6, but for the big 6 / 8 you only get paid even money.
Calculating it out this difference in payouts is directly responsible for the house edge of 9.09% on this bet, compared to 1.52 on the place bet. Translation, this is a major sucker bet, the casino knows placing the 6 or 8 is better than placing any other number, so in an effort to stop it from becoming popular, they put a big fat 6 and 8 in a sexy and easy to reach part of the board, which they collect better off of.
So instead of learning more about the big 6 / big 8, just get familiar with placing place bets.