Bosch GMS120 "Wall Scanner" and "professional" are identical, the name depends on the target market internationally.

Useful precision, Bosch GMS120 is sold under (at least!) Two different names "Professional" and "Wall Scanner" according to its destination market Europe, North America ... (still under item no. 0601081000 Bosch) .They differ that by replacing mode "Drywall" with "wood" with no impact on performance.
Apart from the most favorable Research configurations for which the results are reliable, the device is sensitive to many parameters such as static electricity, humidity, magnetic fields and its direct environment .. indications are sometimes confusing. With practice and compliance with statements generally happens by cross between different detection modes to target so (more or less) accurate metal, electrical cables and sometimes wood (less convincing), but not in all cases .. .and not for sure (in the knowledge that no detector in this category is 100% reliable!) .Before buying, I tested the Bosch PMD10, the operation and the results are finally very close ( the price of the 2 models are sometimes neighbors, as many favor the "pro") and I had the opportunity to use the Bosch PDO 6 simple but effective for those who have only the metal or power cables detect (but limited in depth performance), again the price difference with the model pro GMS100M is sometimes tenuous and worth thinking ...
I acquired from the Skil F0150550AA (Skil Bosch using the technology for its devices, for the story is the clone of Bosch PDO Multi plus distributed by Bosch under its own brand, a shame given its good performance compared to the "pros" models of the "official" ???? range) and can confirm positive tests (eg. short video on Youtube but proven comparative aves Bosch GMS120) that make it probably the best quality / price search detectors, with superior sensitivity (despite a lower depth detection ???) in the metal and cable research, for wood of 2 does not allowed me to find my reliably beams under 1 to 2cm plaster .... I recommend it, even if it is not immune to defects of this type of aircraft, its indications have been more reliable and honest than the "pro" GMS120, for a more contained price. Only regret, the lack of backlight, display less "successful" and fragile felt skids.