Yes, I would say it's comparable, but due to the rounder shape of the speedy and that the antigona is just a little smaller, I would say the speedy fits just slightly more!
Considering the sizes: the speedy is 9.8" length x 7.4" height x 5.9" width, while the Antigona is 8.5" length x 8" height x 5.25". The speedy is longer but the antigona is taller, but the shape of the antigona narrows in a little more at the top.
However, I would say they're both amazing sizes for an every day bag and both fit a great amount of items, so the bigger factor to consider if the design you prefer! They're both very practical and lovely bags. I'm personally a bigger fan of the Antigona than the Speedy although the Antigona is a little heavier; the Antigona seems to keep its shape better as well. The different leathers all seem to be easy to care for. Hope this helps!