I think it's a lot easier to carry an electric and a small amp compared to hauling an upright around.
Personally, i'd go for the Carvin. MM and P PUs on a six string sound intimidating. I'm half tempted to toy around with that building tool myself.
Sorry, I wasn't clear. My current bass is an active six string with soap bar humbuckers. I want to get a five string active/passive with a MM and a P. My current bass sounds a lot like a thick active Jazz because of the pickups and their location. I was debating between getting a P bass and a Ray and then I saw that I could build a Carvin with both types of pickups very close to their sweet spots. I've heard so much good about their products here and elsewhere and I liked the audio demos I found on YouTube, so I figured that I could take a chance with it and send it back if I didn't care for it as much as I thought I would.