Well, Dave and Al were correct. Very different sounds from the two basses. Even with new rounds, the BK was more tame, old school in its tone. Pups are lower output and the overall sound using both pups was mellow, but distinct enough to be heard clearly. I liked the sound and the output was very even across the strings. The bass wasn't overly bassy, the mids and highs were equally represented.
The TJ was altogether different. It has old TI rounds on it and the TVJ pups are way stronger than the Gretsch. The output was clearer and the lows, mids and highs more defined. It has more bite to it, not mellow for sure. So, the TJ can definitely rock out better than the BK. it's nice they don't sound the same! I like them both and could see myself using the them alternately based on the songs I'm playing.
Side bar: BK owners often put TVJ pups in after they hear the difference. A very common mod for this bass.