Salesforce Labs Model Builder is a free app on the AppExchange which permits to upload prepared files to create Einstein Vision & Language models. It's just a UI layered on top of Einstein’s integrated REST APIs.

You can find it on the AppExchange here:
https://appexchange.salesforce.com/appxListingDetail?listingId=a0N3A00000Ed1V8UAJ

In Model Builder :

• You have to use an external app to do the labelling (drawing boxes in pictures)
• You have to save the labelling as a CSV file
• You have to correct the CSV to make it fit Einstein Vision requirements
• You have to zip all the images together
• You have then to upload both files into the Model Builder to get the model created

Model Builder known Limitations:

• If the images are not at the right format/size/resolution the zip won’t be processed
• If the images as too many, you won’t be able to upload it into sliced version of the zip and csv

What SharinPix Labelling App offers on top of that:

• Includes the labelling tool (you can draw boxes from the UI in the pictures without need of external tool)
• Includes a support to get the team working on labelling organized
• Provide QA support and validation around the QA tasks done
• Transform images into lower resolution if needed
• Transform images format into expected format if needed
• Can exclude easily some images, some labels, in order to test different version of dataset/models
• Store each dataset/model information in order to replicate, modify, optimized
• Can automatically slice zip files into different ones if size is too large
• Support already new version of the API as soon as it is available as Pilot

As part of the SharinPix Einstein Vision Apps, you also have 2 other apps beside SharinPix Labelling App :

• SharinPix Review App (review results and permits to validate the quality from real images from the field)
• SharinPix Retrain App (retrain model from reviewed results coming from Review App – Keep track of Model history)

Those 2 options are not available from Salesforce Lab package and are key to get an optimized and bullet proof model ready to go to production.

In recap:

• Salesforce lab package is a nice starting point if you want to test and quickly create small number of images models
• SharinPix Apps are the best option (internally used by many Salesforce SE even used in Einstein Vision team) as soon as you get serious about Model creation/optimization and organized team work around labelling/producing models

Note that SharinPix also offer Services to label and help you on your Einstein Vision projects.