The KAB with your central vac will give you both better suction/lift and on top of that much quieter operation. The Nitty Gritty will be deafening compared to the KAB/C-vac combo. On top of that, if you are cleaning a lot of records at once, the Nitty Gritty has a reputation for being prone to overheating. I would be surprised if Kevin at KAB who sells both products wouldn't advise you to buy the KAB under the circumstances. The one drawback with either, as I've pointed out, is applying fluid. With either one it's a pain and you'll be best, as I've said to source a junk turntable for this.
I would talk to Kevin at KAB and see what his advice would be.