Personally, I love the Antigona. I received a medium glossy black one just a few days ago, and not only is it much lighter than I expected, but it also suits my body. I am 5'8 and thin, and the bag doesn't interfere with my silhouette or vice-versa. Someone with a different body type might find it too bulky/unwieldy to carry, as I have seen some other reviewers mention in other parts of the web.
I find it very comfortable to carry. The straps are perfect for the crook of my arm and the flat shoulder strap is comfortable and doesn't dig into my shoulder as a narrow strap would.
I even pack a dust bag or protective waterproof pouch folded into it in case I am going out to a restaurant or if the weather could be dodgy, and then I cover it up. I wanted a chic bag I could carry documents and ballet essentials in that matched most outfits and I've found it! It also makes a beautiful carry-on bag., day bag, and classy evening bag. I don't think I'd take it to formal events, however.
The things I carry in it tend to be light enough; I can fill the entire bag with relatively light items and it won't make it much heavier or compromise its structured shape, but of course that would change if I loaded it with heavy items constantly. I also rotate it with other bags and clutches depending on the occasion, so I expect it to last a long time. I would definitely carry it every other day, depending what I'm doing.
The design is streamlined, unfussy, and impressive. The zippers open and close smoothly without catching on anything. The medium is easy for me to see into and get into. It helps to have light or brightly coloured things in it to contrast with the dark lining. I suggest transparent pouches for the smaller items, particulary if you have "out of sight, out of mind" tendencies.
Someone on the forum mentioned the smoothe calf type of leather does or seems to have a protective coating as well. I thought I had scratched mine despite babying it so much, and it only turned out to be a small grey scuff mark which I removed completely with a white pencil eraser, making it look shiny and new again!
I cannot speak for the small version; I haven't seen it in person. I've read a lot of glowing reviews about the small Antigona, that it takes up less space and still fits plenty of things. If I got a small size, I would still get the smooth leather one since it seems from other posts that the grained version tends to get easily stained with water and such. A specialist might help get it out, but at the moment, I wouldn't know. You can have it treated with a protective spray.
You might also want to consider what you want/need to carry with you, and compare the estimated dimensions of those items as a group with that of the bag you are considering, to get a better idea.
There are plenty of small Antigona reviews on youtube, as well. It could help you visualise the outcome better. The videos definitely helped me make my choice. The most ideal thing would be to try them on and inspect them at the shops if you still have a hard time deciding.
Good luck in your search for your perfect bag!