I've done it both ways. If you rebuild them yourself, you'll need a bit of patience in getting everything thoroughly clean. Additionally, you'll have to rig up something to get the pistons out. Once one piston leaves the cylinder, you can't get the second one out without sealing that open hole.

Additionally, you've got binding in one.......or both......pistons on the left side. This may required you to use the hydraulic system on the vehicle to remove the piston(s). Compressed air won't be strong enough in some cases.

Then, you have the consideration, after doing all the work to remove the pistons, the cylinder or, more importantly, the piston, won't clean up perfectly. The piston must be perfectly clean bright chrome without any corrosion whatsoever or you'll get a leak. The cylinder needs to be very clean without any raised metal, but it does not have to be perfect.

Sometimes you have to spend an hour to polish the rust on the caliper that is outside of the piston seal and underneath the dust boot. You only have .001" clearance per side. Any slight bit of corrosion will raise the metal and prevent installation of the piston.

So.......what's your time worth.