Not sure why you would expect a dull solid, intended for medium-heavy to heavy oil, to be longer than a polished pearl, intended for medium-light to medium oil.
Smoother, yes, because it will almost assuredly be earlier and stronger, but longer?
Can you explain why you believe this?

just my initial impression from the Brunswick vids, their testers were bowling on 44ft house shot, we bowl on a 41ft feathered out on the backend. I get your point though about the polished pearl aspect. the Nexus just seems a lot cleaner through the fronts with very little polish on it, starting up a little later being a lot smoother on the back end. either way, I will tweak the covers on both balls to get them where I want them and to play well when I need them. don't have ball in hand yet to really know what I got, just excited that I got a barely used Nexus for $37 shipped!

That's a great deal.
I wouldn't look at them as having different reactions, although they do, and should. I would look at them as handling different amounts of oil. The 2.5 handles medium or lighter oil and the Nexus handles medium-heavy and more. They'd complement each other; you wouldn't normally have a choice of using both balls on the same oil condition.

I have a Brunswick Karma black/blue solid and a Nexxus f P+R.

Both are drilled identically for Full Roller and I am a 90 degree axis rotation zero degree tilt Full Roller.

Both balls have been taken to 4000 grit polished.

I bowl on 'very' dry lanes.

The Karma Solid goes very long and has a strong backend reaction.
The Nexxus has a much smoother, less angular earlier reaction but it is harder to control and gets a under/over reaction and rolls out really quick on these dry conditions.

The Karma hits hard and carries, the Nexxus hits weaker and has spotty carry.

Again this is on 'dry' conditions.

The Nexxus is made for more oil.
I got it for when I bowl on heavier oiled lanes.