It's going to come down to the specific engine and application; I don't think you can make a blanket statement that turbo engines are universally less reliable or more maintenance intensive than NA engines or vice versa.
As mentioned I'd want to know whether cam timing is via belt or chain. Chains and their tensioners do wear out, but they are generally at a much longer interval than a belt. A four cylinder engine will generally be cheaper to maintain than a six, and easier to work on. But again it depends on the manufacturer and implementation.
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