Don’t know what algorithm Serato uses, but indeed the one PN uses is very good as it actually does an average instead of “hard” deduction or addition of a few dBs.
I’ll second Younez that it’s best to NOT use the software autogain (at all). It is very good practice to use the trim/gain buttons on your controller to set correct levels. This way you won’t get into trouble if you are using unknown tracks or using other equipment.
Having all your tracks done in PN will take care that everything in your collection sounds about equally loud, still you need to use your ears and maybe adjust trim/gain anyway (depending on many factors like genre, energy level and – not in the least – compression).
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