Hey, Caleb. We replaced most of the balsa in our SJ21's decks with CoreCell. It costs substantially more than scrim balsa; shipping for either costs so much the materials price difference pales.
Balsa is sometimes shipped rolled up, which may be cheaper. Balsa has more compression strength as a material (tho I'd be curious to know if that obtains post-install) but balsa's vertical shear and flexural properties are poor -- it will snap like a soda cracker. I found the CC to be fairly resistant to that, unless scored.
Both will drink a surprising amount of resin; you need to butter them well with neat mix before spreading the thickened resin, or you may end up with a starved bond. And any lightweight core material must still be isolated from water intrusion. CC will absorb a certain percentage of water, & it can delaminate from freeze/thaw just like balsa. The difference is it won't ROT. The balsa around our mast step looked like gravy. That trait alone steered me toward CC, & I am very happy with the result.
Our new-to-us '72 Ballad has some water intrusion problems around the mast partners, foredeck cleat, and chainplates. Its deck is cored with 1" Divinycell. We drilled out a couple samples with a hole saw; even tho the wet plug was over 30% MC when removed, it had very high compressive strength. It dried out in about four days to 6% MC & now seems good as new. I've tried drying out saturated balsa, but the results were not as happy.
Either material is perfectly satisfactory if you keep the water out -- balsa has a slight performance edge in several categories. Let water in, and neither material is happy; balsa suffers most. FWIW, I put cast resin pads and/or phenolic plate under all high-load deck fittings, in place of core. Even if your bedding sealant fails, there's no risk of water intrusion. Little epoxy collars are cute, but under winches, travelers, deck cleats, or around chainplate penetrations, gimme phenolic sheet running an inch or so oversize in all directions.
Yeah it's heavy -- so is a foam or balsa core full of water.