Size Matters Not is available for both PL and NEC. Either get that for NEC and put it on the Sabercore or get The Light for PL and put it on the NB. You really can't accurately compare unless you're listening to the same font on both boards/speakers/sabers. From your previous video, the Champion saber does sound good to me. It could simply be that the fonts on your NB saber are just bassier in general; I know Shameem's (the maker of Size Matters Not) usually are.
There's 3 main factors for sound: the audio amp on the board, the speaker itself, and the hilt resonance. Being a 16-bit audio driver, the SC3.0 should be better than the NBv4 on that front, since the NB is only 10-bit audio. I believe SF's "high bass" speaker is the same 28mm Veco bass that everyone else uses and is likely in your NB saber as well, so those should be equal.
Resonance plays a huge factor, more than people realize. Since SF doesn't install with a chassis (yet), the speaker usually isn't properly enclosed so sound quality does get lost a bit. Was your NB installed with a proper chassis? If so, this could be the issue, and can only be fixed by a reinstall using a proper chassis/speaker holder. The speaker in the SC3.0 saber also looks closer to the flat pommel than the one in your NB saber is; even that little bit of space would give the speaker in your NB saber a bit more resonance. Other than that... I'd chalk it up to simply different fonts.
If you do want to do a reinstall of at least the speaker, the "best" speakers in the hobby, imo, are the ones from Saber Essentials (operates though his Page on Facebook). Each one is hand made and tested in his garage. TCSS has stock of the 28mm 4ohm bass and will be getting in more types soon. I don't see any specs on the SC3.0 so you might be safer with the 8ohm speaker instead of the 4ohm if you wanted to replace your speaker with one of his. These speakers have amazing range on them. While very bassy, the Veco falls a little flat on the midtones.
Here's a link to a
video comparison of the 28mm Veco bass (amber saber) to the 28mm 4ohm SE bass (green saber), both NBv4 and both using KSith's "The Light" font. Due to the solid, rather than vented, pommel on the Consular hilt, the resonance is a little better and the sound is a little bit clearer by comparison... bu the SE blows it away on volume, range, and bass.
And SF usually drenches the threads in superglue. Gonna need lots of elbow grease to get it apart; since the saber is installed I wouldn't recommend using acetone or heat to weaken the glue.