I have a Sadowsky MV5 and a Valenti Reversed PJ. In the past, I have had a Sadowsky NYC reverse PJ, a Metro PJ, an NYC modern and a few other Sadowsky basses.
First of all, it's hard to compare any bass to a Sadowsky Modern. The pickup placement and the soapbars create a very unique sound. Personally, I like it a lot, but the middy grind is there all day, and hard to dial out. Also, the pickup placement really focuses the tone. It is hard to get a "round" tone out of it.
As for the reverse P setup, I think it impacts the tone as I have written on here many times before. In fact, I was inspired to have the Valenti built as a reverse P because of my experience with the Sadowsky I owned. The low end is more focused and less puffy than the traditional config and the highs are a touch fuller. At center detent, the bass sounds, to my ear, more like a modern soapbar bass (with a more traditional PU placement, unlike the Sadowsky modern). When you start panning the PUs, you capture more of the expected J bridge and P pickups sounds. Soloed, I think the front pickup still sounds like a P bass, only less so. I strongly prefer the reversed setup to the traditional design.
The Sadowsky Metro PJ I owned, with traditional PU placement, was probably my least favorite of all I have owned. Of course, that is like picking out your least favorite supermodel. Although, the bass was Alder with a Pau Ferro FB, which have never really cared for in general. Whether it was the woods or pickups, I cannot say, but it was quite "tame" as compared to my traditional view of the Sadowsky tone.
My Valenti is Nordstrand equiped with the 2b preamp. The Nordstrand pre sounds amazing in this bass, but it doesn't have near the coloration of a Sadowsky pre. I imagine if you ordered a Valenti with Sadowsky guts, it would be a challenge to distinguish the two in a mix.