There's a great post called "Quality Time with the V6 & the V8" by kbmuenkel that you might find helpful.
Before I test drove any Genesis, I had exactly the same thought as you: if I could get the same features on a V6 as a V8, I'd take the V6 to save a little bit on up-front cost and fuel. Now I know that my Genesis will be the V8. Here's why...
I've test driven the V6 and V8 back to back on two separate occasions (four different cars), and in my opinion, there is a meaningful difference in ride between the two trims. In the interest of full disclosure, I'm not a Genesis owner yet. I arrived at the dealer this past Sunday with the intention of buying a Black/Black V8 4.6 (which they just got in), only to discover that someone else bought it (paid by their company no less!) about 15 minutes before I got to the dealership! So I took the opportunity to extensively compare the V6 and V8 again, taking each out for 30-45 minutes. The only Black/Black they had left was a V6, so the sales guy was actually suggesting I go with the 3.8 (V6) since it's "pretty much the same" and costs less. I was, and still am, dead set on Black. Here are some observations:
(1) The V8 is noticeably quieter. I'm not saying that the V6 isn't quiet. It is. But the V8 is more so. I noticed that immediately, even when just driving off the dealer lot.
(2) Based on my limited experience above, the V8 is also noticeably more composed, powering through bumps and road imperfections, whereas the V6 felt more jittery and bounced around more. In fact, the salesman (a passenger on both test drives) openly admitted that the 4.6 felt significantly smoother and more composed. Keep in mind that this is right after he was pushing me toward the Black/Black 3.8 we just drove first. He also agreed with me that the engine in the V8 is much quieter.
(3) This is admittedly subjective, but the steering on the 4.6 feels a bit more solid to me. It's not a huge difference but definitely noticeable. OTOH, the 3.8 felt a bit more "tossable" most likely because it's a slightly lighter car, with less effort required to turn the
wheel.
(4) This is not a "ride" difference per se, but the leather in the V8 is much nicer and luxurious, I would say buttery soft compared to the rubbery, rougher feel of the 3.8 leather. The difference is immediately noticeable upon sitting. Well, maybe this is a ride thing after all... ;-)
So, even though I didn't get my Genesis yet, I'm 100% certain that when I do, it will be the 4.6. I liked the feel/composure of the ride, so the extra $2k is worth it TO ME, especially since gas mileage is similar and you get a few more horses under the hood! Needless to say, acceleration from 55 mph to 90 mph is much smoother in the V8!
You should test drive both trims and see which you like better and if the differences justify the delta in price/availability. Ride quality can be subjective, and even different cars of the same trim may ride differently. Who knows? You might even prefer a V6...though I suspect not. ;-)
