Pardon me if my tone is rude, as I don't mean it to be. But I'd be surprised if you are actually recording your vinyl into your Mac at 32 bits. There are no 32 bit A/D converters, not without sophisticated and expensive bit ranging. I am sure your Mbox is 24 bits and your Quattro program is *processing* at 32 bits. Even with a 24 bit converter, typical signal to noise is really on the order of 17 or 18 bits.
Having said that, your Quattro file is greater than 16 bits. I am not sure which program has the better dither. Of course the question is, not only which has "better" dither but which type of dither do you want to hear? There are many types of dither and then different types of noise shaping (if you want that at all).
I would suggest you dither your audio both ways (through both programs) and listen to which sounds better to you.
Barry