from what  I have read most vitaras have 16" wheels and most trackers have 15" wheels.
so I am guessing the vitara has larger calipers and rotors, are they interchangeable with the tracker?

Easiest way to check is go to www.autozone.com and see if both vehicles have the same part numbers.

They are different. I almost changed all my Vitara brakes to the Tracker rotors and calipers to keep from having to run 16" wheels, but i just added enough lift to clear 245/75 r16 tires. You can't find many tires any smaller than that with an aggressive tread was the main reason i wanted 15" wheels.

does that mean you can swap calipers and rotors from tracker to vitara or vise versa?

They are different. I almost changed all my Vitara brakes to the Tracker rotors and calipers

Even then you will have a hard time finding 15" rims that fit. The rims on the "99+ Trackers seem to be special made or something because the 15" rims factory and aftermarket from my "97 Tracker did not fit on my "00 2.0 2-dr or my "04 2.5 4-dr. They hit the calipers.

I have a set of the 6-spoke aluminum rims from a '95 Kick on my '02 Tracker.  There were no problems with fit at all.

I had to run wheel spacers on my after marker 15" rims to clear the brakes on my tracker, but the factory ones were 15"

does that mean you can swap calipers and rotors from tracker to vitara or vise versa?

Yes