So little update: I went to the store today myself to take a look at the Keepall 35.
Size:
It is gorgeous. I love the size! It actually is smaller than I expected, but as it is longer than my Speedy B 30, it looks much more spacious and functional for daily use. It could easily fit my iPad 11 Pro and DIN A4 Sheets or a magazine (putting the iPad 11 Pro in my Speedy 30 requires juggling and is rather painful).
I think I could be fine using it as a overnight bag (I am small 5“2‘, so my things are not as space occupying) and it would have a great size as a carry on luggage for my size!
Canvas or Taurillion:
They only had the Canvas one in store. I looked at the Taurillion one in 25 to get a feeling for it.
Initially when I saw it first online, I thought Canvas, but then did not like the reverse parts on the side as they look quite flashy on the online photos. Only other option is Taurillion. I love a whole leather bag, but was not in love with it on the photos and I don‘t know why, but thought probably it is the better deal for only 400€ more. So I wanted to see both in real life.
Now looking at it, I am definitely in love with the Eclipse Monogram! The reverse part is not as bright in real life as on the web photos and the combination looks very sleek and understated.
The all leather and all black Taurillion one should be more understated, but actually looks more flashy to me because I feel that the embossed logo is more visible. The leather is divine though and the bag very light, so not heavy at all for a leather bag.
Speedy 35 or 40:
I wanted to compare it to those two, but they did not had them in store. I already have been thinking about ordering either a Speedy B 35 or 40 Mon Monogram for that purpose. The Speedy is a but higher than the Keepall and I actually like the leather straps around the Keepall more than the naked middle part of the Speedy. So I was fine with not looking at them for comparison.
Now I ordered the Eclipse Canvas one and can‘t wait to get it in my hands and use it everyday! (The instore one had one of the straps sewed on a bit slanted on one side…)
Finally a good sized all day bag in luggage style!
Sorry for my long babbling, but perhaps it is interesting for those who are also searching for information like myself.

Will post pics when I get it!