According to Stand Wong's "Professional BJ"

Single deck's expected win is $48/hour (well, using his benchmark, bet strategy 10 - 100), and 6 deck is $16.

I just read from "Blackjack Games to Avoid", that the 6/5 game make you short $15/hour. But 48 - 15 = 33, is still more than twice of the 6 deck's expected win. Why everyone says "avoid 6/5 single deck"?

Is this because of the bet varietion? In single deck, the count could go up and down much more dramatically than shoe game, so your bet will spread very dramatically, and can draw more heat.

Or is this beause single deck shuffles too often?

I too wondered about the 6/5 until last weekend up in Tahoe did I have no choice but to play that. My gosh it was terrible up in Tahoe. All table's were minimum 15 shoe or single. All singles paid 6/5. So I sit and the count swings after first hand to +7. I go in with 100, hit my natural and see the pay out. Shocked I almost started saying he didn't pay me enough. I really just wanted to tell this story because I was so happy about the count and my natural. It was however ruined by the 6/5, so stay away.

I have no choice but to play that

You most certainly did have a choice. You could have chosen not to play that game. You could have played craps. By taking odds, the house advantage is better in craps. You could have played video poker. There are many varieties of video poker with a smaller house advantage than 6:5 blackjack. You could have gone home.

Single deck's expected win is $48/hour (well, using his benchmark, bet strategy 10 - 100), and 6 deck is $16.

But that's for regular 3:2 blackjack. It's almost absurd to talk about beating 6:5. You might get $2 an hour with great pen and a 10-1,000 spread.

I just read from "Blackjack Games to Avoid", that the 6/5 game make you short $15/hour. But 48 - 15 = 33, is still more than twice of the 6 deck's expected win. Why everyone says "avoid 6/5 single deck"?

Apples and oranges. Almost anything is better than 6:5. 10 decks ... 20 decks ... ;) Like Boot said, not playing is better.

ETF

I don't understand how they have an advantage in 6/5. The rules of the game don't change just the pay out for a natural. You just don't get as much "bonus" money. Why would I want to play something else that doesn't have good odds to begin with. Craps? My last experience went like this. Play the come, back my odds, number placed, place the 6 & 8, play the don't come, lay down the odds, craps out lose my money. What fun!

When I go to Vegas I generally get in at least 20 hours on the tables. My average bet is $100 and since you get a blackjack about every 20-21 hands, lets say I will get about 4 per hour or 80 naturals in 20 hours of play. Now if I am playing single deck on the strip, they will pay me $120 per natural but downtown I would get $150, a difference of $30 each multiplied by 80 naturals or a cost of $2,400 or $120 per hour.
This amount can not be made up, you say the rules do not change but this one rule change (payout on a natural) makes a huge difference. Hit or Stay on soft 17, DA or D9 or 10, DAS, surrender or any of the other common rule differences out there are extremely minor when compared to this and it is very easy to measure in pure dollars. Their advantage is huge and their promoting of this game is fraud.

The house advantage in a typical single-deck game with 6:5 blackjack is about 1.45%, and 1.39% of that comes from the loss of the 3:2 payout. In 3:2 blackjack, you start to get the advantage over the house at any positive count. In 6:5 blackjack, you will gain a miniscule advantage at around +5 and it will never get as large as it would get in a 3:2 game. It will always be trivial. Simply put, you can't overcome the huge house advantage with card counting, unless you had a deeply dealt game where you could get away with a very large spread, and even then, you could never compete with a 3:2 game, not to mention the fact that your variance and risk would be out of sight. The loss of 60% of the blackjack bonus is not trivial, it is huge. It is the 3:2 payout on blackjacks that makes it a beatable game. Without it, it's just another carnival game for suckers. As I said, the house advantage in craps and many VP games is smaller than it is in 6:5 blackjack.