lots of subs wont play higher notes well regardless if u tune 28hz or 35hz, they just drop off too fast
but take a sundown sa-12, both boxes 1.75 cubic feet, 600rms, one is tuned 28, other 35, the difference at 60hz is 1db, the higher tuned will play it louder obviously
but the box tuned to 35hz peaks at like 40hz. a 40hz tone would be 2 db louder than the 60hz would be. where the 28 tuned box plays every note less than a db of loudness from 28hz to 100hz.
of course thats all before cabin gain, which screws it all up, but my truck peaks at 40hz, so i do a 35tuned box, my 40hz tone is gonna be 3 or more db louder than my 60hz tone