It depends on the job. 99% of the time I'll let Aperture generate the PSD.
That PSD will be based on an 8-bit JPEG if I'm going to be batch processing a large number of small images (for example a wedding, commercial event, or corporate headshot session where I've photographed 60 different people in 1 day).
However if I'm delivering a small number of commercial images that need to be of the highest possible quality then I'll use either 16-bit JPEG or 16-bit TIFF and process each one manually.
I generally try to avoid using TIFFs unless the payment I'm receiving justifies it.
My photoshop workflow is completely non-destructive, so there is no discernable improvement in quality that justifies the massive increase in filesize. However using TIFFs does slow down your workflow and therefore cost you money.
Can you batch export from aperture into Photoshop?