I've been to Reno several times on business trips for a casino company, so I always stayed at that casino. I've had business meetings at Donner Lake and Lake Tahoe, and driven through Truckee a few times. Based on that, I'd guess the wives would have a far better time in Reno. Most of Reno's casinos are clustered in a small central area that is rather seedy and can get a little spooky at night. I suspect they might enjoy the suburbs a bit more, where there are nice shopping centers, restaurants, etc.

Truckee is a smallish mountain town, Donner Lake offers little to do other than look at the lake. Lake Tahoe has casinos on the south end, but very little else.

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