The WK is certainly a bit more refined, and has more of a "new car" feel. I personally prefer the more high-end-90s-American feel of the WJ to the WK. The real deciding factor for me though, was the incomparable looks.
Since it's generally agreed that both the I6 and V8 are good engines, it's a matter of preference. They both get the same mileage and cost the same these days, so the extra power was a no-brainer for me. However, between the 4.7L HO and 4.7L, I didn't feel a justifiable difference in power to make the much-less-common HO worth holding out for. So in my opinion, if you find the perfect Jeep for you with a HO, go for it, but don't make the standard 4.7L a deal-breaker. I'm very happy with my standard 4.7L and its torquey low-end. In my test drives, the I6 took all the fun out of the WJ.