I recently acquired a Canik Shark C which is the same gun as the TriStar T100, but while I've had my hands on several CZ 75 compacts, I can't say I have any actual experience with the C100 so I probably won't be able to answer your questions fully but I'll throw my $0.02 at it in hopes of helping.
First off, both the C100 and T100 are produced by the same company (in the same factory) and are based off the same platform, so they're going to be very similar.
The t100 version safety makes me think it is a decocker rather than a safety? Is there any significant differences between the safety functions between these two?
Nope, no decocker. Safety should be about identical to a C100. Only difference from a standard CZ 75 is that it can be placed on safe with the hammer down (I'm 98% sure this applies to the C100 as well).
Is the safety inherently stiffer on one model over the other? How about trigger pull.
The safety on my Shark C was pretty stiff out of the box but has loosened up nicely after a single trip to the range and about a week of fiddling with it on the couch. It is still a little stiffer than a CZ safety, but it's functional. The trigger actually felt a little better out of the box than a CZ IMO, barely detectable creep which is only noticeable if you're looking for it.
Again, I have not gotten my hands on a C100, but as they are made by the same company and are derived from the same platform, I'm going to guess that there is not a significant difference in the safety or trigger pull between the two.
I like the smaller appearance of the c100 slide stop and safety over the t100. Are they interchangeable perhaps?
Perhaps, I honestly wouldn't be surprised either way.
So what are the actual differences between the c100 and the t100?
Given that they're manufactured by the same company and are both based off the CZ 75, they're going to be very similar and the aesthetics are probably the biggest difference. Both have alloy frames and a stainless slide, presumably an identical or nearly-identical DA/SA trigger as well as safety, they even take the same mags.
The T100 has a slightly shorter barrel (reported at 3.7" for the T100 and 3.9" for the C100, although I could have sworn that another reference listed the T100 at 3.9", I can check on this when I get home) The T100 MAY have a slightly shorter barrel
, see EDIT at the bottom, the C100 is offered in .40S&W as well as 9mm while the T100 is currently available in 9mm only. That's about all I've got.
I wouldn't be surprised if someone posts some gigantic glaring difference that I've missed and makes me feel silly, but I really do think that they're different iterations of the same gun with the C100 having a more "classic" look and the T100 being a little more modern. While you may see more C100's in circulation currently, this is probably due to numbers imported more than anything else; I'm pretty sure the C100 has been available longer in the US than the T100.
I'm very pleased with my Canik Shark C. It feels great in the hand and has so far shown itself to be as reliable and accurate as any semi-compact handgun I've handled. The slide catch, safety and mag release were all a bit stiff initially but they've improved a lot with just a bit of tinkering. My only complaint as far as craftsmanship is that the grips and sights are made of chintzy plastic.
I don't think you could go wrong either way and, ideally, I'd say shoot 'em both and see if one feels better, but obviously I recognize that this is often not possible. If you've narrowed it down to one or the other and can't choose, I hate to say it but I'd probably base the decision on looks (and price difference if applicable).
Hopefully someone who actually owns both will be able to chime in and give you a little more detail.
EDIT: I'm trying to sort out this discrepancy in barrel length... I didn't even think about it before but the 100 in both names refers to a 100mm barrel (3.94"), but TriStar's website lists the C100 as having a 3.9" and the T100 as having a 3.7". Canik 55's website says both guns have a 100mm barrel and several other sources I've come across indicate a 3.94" barrel for the T100. I get off at 8pm EST and will measure tonight to sort out this silliness.
UPDATE: My barrel is 93-94mm, or 3.7 inches, so it may be a little shorter.