When a set helps
For long or very large plates, a single vacuum lifter is often not sufficient, because the plate rotates around the suction point. Two devices stabilise the load and make the rotation controllable.
Two gripping points are also an advantage during cutting, when transferring to the cutting table and when inserting into tight spaces.
When a single device is sufficient
For individual tiles up to about 60 x 60 cm, for short transport distances and for small plates, one vacuum lifter is usually sufficient. If you only work occasionally, one device is often the cheaper option.
What to look for in sets
Verdict
A set is advisable if your plates are large, long or sensitive, or if you regularly work in pairs. For small plates and infrequent use, a single vacuum lifter is sufficient.
This guide is editorial and general. For safety questions the manufacturer datasheet applies.