I love Miele for some things but here from a functionality standpoint a GE Advantium 240v is the better option for cooking performance.

I have had the 6000 M touch series speed oven for almost 9 years. I use it mainly as an oven as I rarely microwave. The 7240 is very basic. It lacks several oven modes like surround (the mode I use most) and intensive. The 7640 has many more modes and I would definitely step up to that model. The 7840 has some additional bell and whistles like motion react and probably more auto programs. I don't find the auto programs on my speed oven useful. I rarely use the combination micro/oven mode as speed cooking is not a concern for me. I do find the auto programs very useful on my CSO and 30” wall oven. I suggest looking at the owners manual for these models and read about the oven modes and decide which one best fits your needs.

I did a compare between the two higher end models - one is their pureline and the other is their vitroline which is more expensive. There does not seem to be any operational differences. I have the pureline in my kitchen.

Kim, does that mean there are just aesthetic / visual differences between those lines?

For the most part yes - the Vitroline only come in gray. The pureline has some choices. There are a few other differences but nothing that would drive me towards the Vitroline unless that was the line I wanted in my kitchen. Here is the comparison between the two. Differences only are noted: Miele 7640 7840 Compare

"it's really hard to tell online"

1. Browse here: https://www.mieleusa.com/e/compare/11804480,11804600,11804630
2. Scroll down until the photos of the appliance drop down at the top of the webpage.
3. Set 'Only Show Differences' at the upper-left to "Off".
4. Now you see all the features of the appliances for comparison.
5. The sections Convenience Features and Operating Modes show the greatest differences among the appliances.
6. The differences between the 7640 and 7840 appear to be trivial and not worth $700 (list).
7. Read the 7640 user manual to decide whether the features absent from the 7240 are worth $900.

The Miele PureLine DirectSelect Series H6200BMBRWS ($1500) doesn't appear on the Miele USA website but is available.