Fixed focal length cameras have a slightly sharper image, but varifocals are like a manual zoom, great for a beginner that is not sure of what they want or what they need. The biggest mistake I see people do is expect to cover the widest area possible without regard to pixel density. So they go for the 2.8mm lens, get a 100 degree viewing angle but then complain when they can't ID someone 20' away with a 3MP camera. So if this is your first higher end camera, pay a little more, get the ds-2cd2632 bullet and spend some time adjusting the lens, seeing what works for you, what doesn't. This takes time to figure out and understand the compromises. I say get the bullet because it's way easier to install, focus & aim. Domes can get tricky, you have to take them apart to mount, to aim, to focus, heck, almost impossible to focus the ds-2cd2732f without moving the lens out of the way to focus, but when you do that you can't easily focus, so I would avoid a dome as your first good camera. Also domes have annoying reflections from the sun, from shiny objects. IR light bleed can also happen with any dome if not set right when putting the dome cover on.
When you figure out what's best for one location, get a less expensive fixed focal lens camera, move this bullet to another location, makes a great test camera. As much as domes look better, out of 9 cameras at my house I have 3 domes, one inside, one in garage and one at my front door.