What's the difference between Einstein and DESelect Engage?

Within Journey Builder in SFMC, 2 Einstein components are available:

1. Einstein STO

Einstein STO provides send-time optimization, which allows sending a message to a contact when Einstein thinks the contact is most likely to open a message, within a timeframe that you define.

It's possible to continue using Einstein STO in combination with DESelect Engage; first, you put a DESelect Engage component in the journey to decide if a contact should receive a campaign Send (also referred to as just "Send/s"), next you have Einstein STO figure out the exact timing of the Send.

2. Einstein Frequency Split

Einstein Frequency Split is a simple saturation control solution, which considers contacts over- or undersaturated based on previous engagement data of a contact. 90 days of history and the use of the SFMC subscription center are required for this to work.

Black box

AI is used to make the saturation control decisions, so the logic is a black box, hence no feedback is provided on why a contact is considered oversaturated.
Engage provides a detailed prediction and history of which contacts will be excluded from which Sends and why.

Saturation control rules

Einstein does not allow defining your own saturation control rules. In Engage rules can be defined up to the level of contact categories, campaign types, and channels.

Send prioritization

Einstein does not offer Send prioritization; it only takes the past into account and has no capability of looking ahead at other Sends that are planned in the future.

Engage offers a campaign calendar where you can plan future Sends and assign them priorities. Engage looks ahead in the future at planned Sends to reserve timeslots for the most important Sends.

Accuracy

Einstein considers a contact over- or undersaturated for a whole day, as data view data is processed only once per day. So while a contact may be undersaturated at the start of the day, as you send messages during the day, the contact may actually become oversaturated but Einstein will only detect this the next day.

Engage does not consider over- or undersaturation on a contact level, but on a Send per contact level. Hence, a contact may be excluded from Send 1 and 2 but included on Send 3, even if all these 3 Sends are sent out on the same day.

Supported channels

Einstein supports Email and MobilePush.
Engage supports Email, MobilePush, and SMS as native SFMC channels, but can also process custom channels, even if those Sends are happening outside of SFMC.

Hosting

Einstein is hosted on AWS, which may be a concern, especially for retail customers.

Engage runs on Google Cloud.