Whichever strategy will get you the most EV in any particular situation. Consider, for example, that you're at a major casino with plenty of shoes, but you've found a dealer who deals at lightning speed and you've got the table heads up or with only another player or two there. What's the answer? I would probably stay and play all and employ as enormous a spread as I can. You see, these types of things are just glossed over in the books, with their tables of expected hands per hour for a given number of players at the table. Generally speaking, trying to find a dealer who deals significantly faster than other dealers is superior to Wonging out or backcounting.
The answer to your question also depends on your entry and departure points. I don't really advocate moving around the pit or casino with aggressive Wonging-out or backcounting, but trying to find the pit or dealer with the best conditions. If you absolutely must bounce around, you can certainly reduce the spread by requiring a positive edge before jumping in and leaving at your best estimate for the ODP. But, again, all of that stuff is for minor-leaguers. Far better is scouting for the best conditions, remembering the names, shifts, and so on of dealers who deal and shuffle extremely fast and being surgical in how you target shoes. You can literally double your long-term EV this way.
In determining if a pit is better than another pit in a major house, you first look to see which pit has the table with the biggest action. You then position yourself at a table at which it is inconvenient for a boss to pay close attention to you in the same pit, because he'll have to track and observe the big player's play closely. Keep your max bet below the big player's bets, and you won't get noticed very much. Secondly, you look for pits where the bosses definitely don't remember you or, if they do remember you, it is because you got destroyed the last time you were playing there, and they think of you as a loser.
These things will take you much further than worrying about when to Wong in or out of a game or what spread you should employ when using different approaches. If you find a shoe with great conditions but where the count gets intolerably low, you can always Wong out to the bathroom for a couple of minutes and then come right back for the next shoe.