Burst transfer from memory to Nios II

When the master and slave are perfectly matched in terms of width, max burst count, and burst wrapping capabilities then there is no overhead in SOPCB or Qsys.

When burst adapters must be inserted in the logic due to a mismatch there is no overhead with the adapters in Qsys (there is overhead in the ones for SOPCB though).

So the only cost is the additional logic in any burst adaptation logic that Qsys might need to insert along with the extra logic in the masters to perform the burst. If you require burst adaptation logic it's possible that the master provides a suboptimal burst for the slave interface you have built. I don't know what your slave is so I can't say for certain.