Hi R.karoff

Thank you for your question. Here at Galaxus you have the option of comparing individual devices with each other. Simply call up the respective device and add it to your comparison list ("Compare" button directly under the "Add to shopping cart" button). We will also be happy to explain further differences between the three devices here:

Roomba i3/ i3+
10 times the suction power*.
Gyro Navigation
Drives even in the dark
1800 mAh Li-ion battery
Two counter-rotating rubber blades 18cm long
Very low height of only 9.25cm

Roomba i7/ i7+
10x suction power*
VSLAM Navigation
Requires minimal light
1800 mAh Li-ion battery
Two counter-rotating rubber blades 18cm long
Stores up to 10 cleaning maps (e.g. per floor)
Rooms/areas can be marked and named in the cleaning map
Room-to-room cleaning possible (desired rooms can be cleaned in any order)
Blocking and cleaning zones can be drawn in additionally
Has object recognition

Roomba s9/ s9+
40 times the suction power*.
VSLAM Navigation
Requires minimal light
3300 mAh Li-ion battery
Two counter-rotating rubber blades 24cm long
Stores up to 10 cleaning maps (e.g. per floor)
Rooms/areas can be marked and named in the cleaning map
Room-to-room cleaning possible (desired rooms can be cleaned in any order)
Blocking and cleaning zones can be drawn in additionally
Has object recognition
Has a carpet turbo mode

All three models can be controlled via the iRobot Home App or by voice command using Alexa, Google or the Swisscom Box. Schedules for regular cleaning can be set and seasonal recommendations received via the iRobot Home App. All three models are able to pair with the Braava jet m6 mopping robot - automatically vacuuming and then mopping if desired. Ideal for allergy sufferers are the models with automatic extraction station (i3+/i7+/s9+), where the dirt is transported directly from the container into an anti-allergen dust bag after each cleaning.

Please note that iRobot is always looking to improve the iRobot Home App and add new features. This benefits not only new Roomba or Braava owners, but also those who already own a device. So the Roomba and Braava models are always learning and adding new features from time to time.

We hope we have been able to help you a little. Otherwise, we would be happy to advise you directly by phone on +41 62 746 06 74.

Best regards,
Your iRobot Team

*compared to the Roomba 600 series

so if you compare it like this, i7+ is the better choice for the same price? and even more scope of delivery than i3+.