1) What is the difference between SSD4 and Trigger?
A: Please watch the video below:
SSD4 is a MIDI based sampler (virtual instrument), where as Trigger is a Drum Replacer.
2) What samples are included in Trigger 2-Platinum? What samples are included in Trigger-EX?
Please view the following: Steven Slate Drum Locker
3) What is the difference between Trigger 2 EX and Trigger 2 Platinum?
Aside from the additional library samples that come in Platinum, the Platinum versions unlocks the "Gate" function. Here is an article the provides more information regarding the "Gate" feature in Trigger 2 Platinum: Trigger 2 Gate