As per my knowledge, the VCD file is the IEEE standered defined format for the waveform dumping, so it will be supported in all the simulators and waveform viewers. While VPD is the Synopsys standard for the waveform data base, so it will be supported by only Synopsys tools. VPD size will be lesser than the VCD file so, better to use VPD if you have Synopsys tools(e.g.VCS)
VCS contains only the signal activity while VPD/SHM/WLF/FSDB - all binary formats from various vendors contain lot more debug information (such as drivers etc.). It is best to use the binary format and if needed convert it to VCS via:
wlf2vcd is in modelsim. As wlf file is generated by the modelsim. VCS won't be having it as, Synopsys has nothing to do with the wlf file which is proprietary to Modelsim.