I'm assuming you have an H23A1 in your Prelude Si, or you have a base model with the F22A6. Because if you had a H22, you wouldn't even be mentioning the other options.
My opinion: turbo what you've got. It's simple to move from an F22 up to an H23 non-vtec(the turbo kit will need no mods/changes whatsoever), and I'm not convinced an H22 has much advantage in a turbo setup, considering all the extra expense.