PD user here, bridging the gap to Max/MSP
many objects are similar, some are different, some you will find missing.
if you are looking for replacements for the complete pd-extended externals you probably have t spend a few weeks and write your own.
one major difference is that in max you have integer numbers, too, and sometimes it is important to be aware of the difference.
There is a lot of differences, especially between GEM and Jitter, but in audio domain too.
For visuals (Jitter) I recommend do not trying to reproduce GEM/PD patches in Max, but rather - due totally different architecture - learning from basics.
Patching audio is a bit more similar in both environments, but not as much as you may expect. A good example is lack (on Max side) of interpolated basic buffer player (such as tabread4~ in Pd). But on Max side you may use - instead of mentioned tabread4~ - a simple gen~-based solution. Gen~ is, from the other hand, very unique Max DSP feature (a bit corresponding to NI Reaktor's "core").
Maybe a good idea will be to compare Pd and Max examples to check how the same problems are solved on both platforms.