The Designer allows you to adjust the blade up and down to half a gauge. So a 1guard becomes a 1.5guard. The top Oster clippers do not have that option, which is why my recommendation is best for those just starting. After some usage, you will notice that make louder hmms than other clippers. This is not a problem. Maintaining any clipper and trimmer requires regular cleaning (for every 20-30 clients). This is your money making tool so take care of it. Use a screw driver to remove the screws and have a brush ready to gently remove hairs between the blades and insides. If you happen to adjust the blades too tightly, the blades will create an extremely loud ring when turned on. Not to fear, just take your trusty screw driver and loosen the screw while your clipper is still on until you hear no more ringing (located on the side) and that should resolve the problem. Make sure to oil your blades after each client to ensure lubrication for longer lasting quality.
As for the Peanut, after each client, make sure to remove the blade and brush the hairs out to prevent clogging of tool and add a drop of oil to the blade after each client.
If you have any questions of maintenance of these tools, post on the comment or just ask your instructors.