From my experiences, yes, and Id be surprised if many people who have owned an '040 based bppc disagree. For me it was all a massive disapointment and this is with a voodoo3 card and soundcard, which is much nicer than aga. The only things that I enjoyed that ppc bought to the table were a couple of emulators (snes, megadrive, mame), ppc video players (still not great, but 320x240 low quality .avi videos (or thereabouts) played reasonably), some ppc datatypes, and ppc ahi. Oh there was also a couple of ppc scene demos that are quite nice (although no better than what was available for 68k).
As for the 175mhz card, downclocking to 166mhz helps a little (assuming the 68k cpu will do 33mhz), or failing that overclocking to 180mhz will also help (33/30mhz bus respectively). Quite a big jump vs the default 25mhz bus that the card comes clocked at. Bus speed and ram speed are more important at these sorts of speeds than cpu clock rates.