275 degrees isn't really "Hot and Fast." It's a good place to start though; especially with briskets or short ribs.
But since you asked, a brisket cooked more slowly has a different flavor than one cooked much hotter. Briskets cooked slower/longer have a slightly "sweeter," more complex quality to the smoke (even when using oak/pecan/almond). That quality seems to diminish and change slighlty the hotter you cook. Briskets cooked really hot on a drum or WSM (with no deflector/pan) can take on what can best be described as a slightly "grilled" character. This is to say, both temperature and the type of cooker can affect the flavor profile (along with the type of wood you use).
If I'm cooking for guests (serving brisket), I'll cook the brisket much slower (250-300 range). However, if the intent is chopped, sauced, or incorporated into another dish (enchiladas, tacos, chili, etc.) then I let 'er rip.
The fastest full packer (12-14lb) I've ever done from start to finish was 3:37 (from the time it hit the pit (including time to wrap) to when I pulled it off to vent the foil and rest). That rocket fast brisket was really good (and perfectly tender). Nowhere near as complex as a 15 hour brisket, but I lit the pit after my second cup of coffee and was eating brisket at lunchtime.
I felt like Cool Hand Luke at the end of the "Tar Sequence."