I use the Tamiya acrylic clears for most of my clearing. It's a decent clear without the glaring, unrealistic shine that some clears seem to have, and it is safe over everything, and is non-yellowing. I will sometimes use Alclad clears, mostly because I just happen to have some on hand and the results look good, but they are lacquer, so may react with enamels.
However, having said that, I don't use clear coats on many builds if the paint is a solid colour, and most of my builds are solid colours. On metallics I always use a clear.