When replacing a caliper you can buy a bare unit or a loaded one that comes with the bracket. Loaded costs a little more - so is it worth it? For most people, yes. Here is the case for loaded calipers.
What you save
A loaded caliper comes with its mounting bracket already attached, so you do not have to transfer the old bracket or fight seized, rusted bracket bolts; see what is a loaded caliper. That saves real labor time and the frustration of broken hardware.
Fresh slides mean quiet braking
A new bracket means fresh abutment clips and clean slide surfaces, which prevents the pad binding and noise that a corroded old bracket causes; see high-mileage calipers. It sets up an even, quiet install.
When bare makes sense
If your existing bracket is clean and rust-free and you want the lowest price, a bare caliper can work - you reuse the good bracket. But on any older or salt-belt vehicle, the loaded unit is usually worth it; see sticking caliper.
The verdict
For most replacements - especially higher-mileage cars - a loaded caliper is worth the small premium for the time and hassle saved. Replace pads and service the rotor too; see when to replace a caliper. Fit quality pads and hardware.