As some of you know, this field can get a bit subjective. I'll try to stay as focused as possible.
Without going into many details, you should be looking into 2 things.
- the reaction of the compressor
- the colour that that reaction might add.
By this i mean (and we'll have to look at analog gear for a second here):
There are many types of compressors; namely, the mechanism that allows them to react to the change in level above the threshold. Let's try and make this simple:
- Opto compressors (optical compressors) use a light emitting diode (LED) and a photocell. These are, by design, slower and less "abrupt".
- FET. Using transistors, these guys can have a high impedance input design. You have your famous 1176 on this category. IMO, these guys can be extremely brutal.
- VCA use a voltage controlled amplifier. For this reason, they are usually really clinical, precise.
Ok, now.. all of these can have different behaviours. You can probably begin to see a pattern here if you happened to play with some of these before. If not, Logic has an emulation of these and other designs on their integrated compressor.
I believe that opto compressors can be easily "disguised". Maybe the "creamier" you used? some coloration but nothing much. They can get a bit out of sorts when pushed harder. They won't be very exact either.
VCA are usually really clinical like i said (maybe my choice for vocals? Think SSL G series bus compressor or dynamics). When pushed hard they are... interesting (then again, I listen to a lot of heavy compressed stuff :P)
FET bring, from my experience, loads of colouration to the signal. The design itself brings some limitations (the 1176 was 600ohms input - which will bring some coloration right at the input stage for impedance mis-matching) and they are a bit brutal. Strangely enough, they seem to do a really good job when pushed harder but it can vary on the models a lot.
On a digital domain: Well - a lot of manufacturers are going to great lengths to emulate some of the precious compressors that became legendary (fairchilds, old neves, UREI's, old DBXs etc).
Hmm i guess my answer is getting a bit convoluted better see some feedback or if other questions arise and we'll take it from there.