In handheld and tabletop mode, the performance continues to be impressive with no real noticeable slowdown during gameplay. (switchplayer.net)
There is sometimes some very noticeable slowdown on the character select screen on both story modes - this is most likely from the character pics being animated. (gamerstemple.com)
I say mostly stable frame rate because there are random moments of heavily noticeable slowdown. (cultureofgaming.com)