It's just hard to say. If SQL Server doesn't need any of those columns, but still thinks the first column is useful, it's more likely to get for the smaller index because it's smaller, even though they're the same. As Steve says, you can evaluate this stuff, bit it's not a hard and fast rule. There's no simple formula that points out this index is bad and this one is good. You can look to your code, your execution plans, the usage statistics, and evaluate from there.