What’s the difference between mb star software versions

I have a 2007 ML63 and am looking to purchase a 2004 / 2005 S600 soon and wanted to get one of these units to scan the ML as well as use it for pre-purchase inspections.

From all 921 posts (!) that I read, I am still not sure if I should purchase:

1. MB Star C4 – Link to Seller
2. SD Connect C4 – Link to Seller

I don’t have a laptop yet so I am open to either unit and given that option 1 above is $200 cheaper, as long as it works will all cars, I cant see why I wouldn’t go with this one.

What’s the difference between mercedes diagnostic software? 2019.05 versus 2019.07 from seller OBD2Tool.com

Does anyone have any opinions either way?

Also, is it possible to download the software and load the image directly onto a Dell 830 (or similar) instead of having to purchase a pre-loaded HDD?

Hardware Units:
1.  Mb Star C3 is for all 12V benz cars before year 2014 and some models after year 2014.
2.  MB Star C4 and red C3 are for all 12-24V benz vehicles before year 2014 and some models after year 2014.
3.  SD Connect C4 is for 12-24V benz vehicles from year 2003 to now. It also has WIFI function.