There is core-bond, poly-bond, nida-bond, james bon... no wait, that's not right. There are many different bonding materials out there, some use BPO paste, others use MEK-P as catalyst. Even smushing down into some soggy mat works pretty swell.
I've never used the Nida-bond so I can't say with any validity how it works.
Core-bond uses BPO paste and is real purdy depending on which color of paste you choose (blue works pretty good, the green sometimes is too pigmented so it shows through on thin light-colored gelcoats), it is somewhat thicker being more akin to super creamy peanut butter when you trowel it on your surface. Pretty good work time, you can mix up a five gallon pail and go to town coring a top with a 3 man crew. One to run the gun to wet out the core material and two to trowel and apply the core. Big heavy rollers are your friend with this material, don't worry about filleting the edges or pockets that need filling, you can just slide your blade over it and be done. Sands easily for surface prep. Smells not terrible.
Poly-bond uses MEK-P and is either an off white color (if you use clear MEK-P) or pink if you use the red MEK-P. More like mayonnaise in consistency and you can tune up the cure time just like you would with resin (just add more catalyst, laughing manically while playing chemist is totally up to you). Same deal as before, heavy rollers to set your core material do wonders for the project. The little spits and spats that come up as you do the edges of your core and deposit them on the scrim sides can just be rolled out, no need to drag the blade across the surface. Mixes really nicely with the resin, since they both use the same catalyst - core-bond seems to slip and slide around when using this technique. Building up ramps and fillets for your core doesn't always work out for big areas and thick cores, due to the fluid nature of Poly-bond but it can be done. Sands pretty good, but given the ease of just rolling it out on the material you shouldn't find yourself in a position where you need to sand. Smells like every other MEK-P catalyzed product, mmmm; styrene.
When de-coring areas, the pro-bond trips the de-coring tool up more often than poly-bond. Can slap you right out of the hole and across the surface of the exterior forcing you to do some gelcoat repair.
I think poly-bond gets a little better hold on the core material only because it cross-links better with the resin - same catalyst after all. You can usually pop the entire plug out with core-bond, you have to worry the pieces out with poly-bond.
Both taste horrible and the dust makes you sneeze.
Additionally, since it's MEK-P and you're just guessing how much catalyst to use it's easier to whip up another batch of poly-bond to complete the job than it is with core-bond. BPO likes proper mixtures otherwise you have some fancy (and rather hot) boat art when it kicks off while trying to use it.