Platter density does more for performance than RPMs, there are 5400rpm drives cables of 200MB/s+ (on the outer sectors), older 7200RPM drives can be much slower than that, obviously if you compare same density with different RPMs the 7200rpm wins, e.g.:
Older WD Green/Red/Blue that used 1TB platters, like 1, 2, 3 and 4TB models, speed starts at around 150MB/s and ends at around 80MB/s.
Toshiba P300, same 11TB platters @ 7200rpm speed starts at 200MB/s and ends at around 100MB/s.