Having owned and driven a fair number of ferrari, porsche, lotus....and a CAV GT40 I can share a few insights...
The SPF and CAV are both wonderful cars, but both are nowhere near anything like a production car.....ferrari, porsche, chevy or prius. Both are highly custom cars built in low volume production with lots of teething issues when new from the factory, and nowhere near the comfort level of other exotic supercars. Weather protecion? Nil. Storage? Nil. Comfort? Nil. Sound abatement? Nil. I wouldn't consider a GT40 from either SPF or CAV (or any other manufacturer) as a comp for a ferrari or porsche or lambo, for example. Gallardo? Forget it, no comparison.
You should go drive a SPF and a CAV and form your own opinion, and see if you (and your passenger) can stomach the lack of civility. You'll probably be surprised how raw these cars are. Personally, I loved my CAV and really enjoyed the raw experience, and (relatively) simple mechanicals...and didn't mind the lack of creature comforts at all...for short-ish trips. I certainly would not want to do a cross country trip in my old CAV, but a run to HomeDepot to get plumbing supplies? Heck yeah, it's an event in your GT40. A very fun event.
As far as comparison, they're both great. The SPF is very true to the original design, so it's much more accurate than the CAV is if historical accuracy is your thing. Personally, I liked the stainless steel chassis of the CAV (I live in the rainy Pacific Northwest, and I drive my cars in the rain), and the interior seemed a little more liveable. But again, go form your own first hand impression.
Good luck with your choices!