You cant really use a HP number as a scale, it depends alot on how that # is achieved. a 400 HP motor for example useing typical TRW or Speed Pro pistons is going to be a heavier rotating mass than say Arias, Ross, SRP type pistons,that extra mass will be more critical(not to say TRW or Speedpro pistons are bad, just there not very light). same goes for the rods.
it also depends on the RPM range. If your building a motor with decent compression ratios & nice flowing heads, you may not have to buzz it nearly as high, same goes for maybe using a roller cam verus a flat tappet cam.
It also depends somewhat on how hard it has to work, if its a light vehicle ,with less load,it wont have to work as hard as say in an Impala...or a truck that tows alot of weight.