I went through (am going through?) the exact same deliberation, as are probably many others lurking on these forums. I drove a Model S 100D (Tesla-stated 0-60 4.1) and felt as though it had plenty of punch to keep me satisfied. I then drove a 3 RWD and was disappointed relative to the S I just drove. I was expecting it to have less punch off the line than the S100D, but still punch. Instead, the power delivery ramped-up rather than punched. At-speed acceleration was still snappy in the 3.
I hemmed and hawed, and eventually ordered a 3D after reading Deuce24's review (the first on TMC to write about that model) of his 3D. He stated there was no 0-20/30 lag, and the 3D had far more punch than the 3. Based on those statements and the Tesla-stated 4.5 second 0-60 for the 3D, it sounded probable that I would be satisfied with that version.
I was then debating between switching my black interior to white, and headed to the dealer to see them both in person. Guess which car had the white interior? And guess who test drove that P3D against all better judgement? Although I was concerned about being tempted to upgrade, I wanted to see both bookends (3 and P3D) to try and figure out how the 3D might feel. As many have mentioned, the 3 and P3D are two different driving experiences, from an acceleration point of view. The P3D is an incredible car and I definitely got out of that thing wanting one. Like you, I've been trying to virtually figure out how the 3D will feel comparatively. We all know the numbers, but that's different than the feel. I have a Cayenne Turbo with a 0-60 of ~4.7 (similar ballpark to the 3 and 3D), but how it gets there feels WAY different than the 3s. I know, ICE vs electric, but the point is the feel over the numbers, and the numbers don't always tell the story of feel.
This decision would be far easier if there were 3Ds to test drive. In the meantime, forum chatter will have to do.