The Jacks or Better category is named for the lowest paying winning hand – a pair of jacks or better. Each game in the Jacks or Better category has a pay table with all the same winning hands as the original Si Redd produced game. They are the royal flush, straight flush, four of a kind, full house, flush, straight, three of a kind, two pairs, and a high pair of jacks or better. The games also all play similar to the table game of draw poker, that is, five cards are dealt, the player can discard any or all of them and the discards are replaced with new cards.
10. Low pair (two 10s or lower). Most new players keep a single jack or better rather than a low pair, and it's true that keeping that one high card will result in more frequent winning hands. But most of those will be 1-for-1 payoffs for a pair of jacks or better. Keeping the low pair will result in more two-pair, three-of-a-kind, full-house, even four-of-a-kind hands.
Despite the importance of finding the best machines, most players don't. That's why casinos can offer both decent and lousy machines in the same casino and be confident that gamers will still play the lousy ones. They have to keep some good machines, otherwise they'd lose all the players who know what they're doing. But most of the machines will be bad, and most gamers will play them anyway. Heck, in Vegas even casinos and supermarkets have video poker, with absolutely terrible paytables, but people will still play them rather than going across the street to a casino where they can get seven times better odds. Go figure.