I know that Colonil's Waterstop has been a great product for many bag owners.
I think its effectiveness depends on the leather. I actually did a test with my Pandora but the leather is so "unfinished" that the spray didn't seem to have any effect. However, I have tested the spray on at YSL Chyc and it made the water bead. I have also sprayed some of my Balenciagas with it. A Mulberry owner treated her bag and she ran water from a faucet over her bag! The leather was fine. Like the Antigona, these bags have a certain amount of finish/glazing on the leather surface. My pandora is pepe and lacks that solid finish of these other bags. I think that makes the difference.
Of the stuff I have tried Colonil Waterstop really seems to have the most water repellancy and didn't affect the color or texture of any of my bags.
If you decide to try, do a test on the bottom panel and flick some water and see how it does. Also, allow a good 48 hrs to dry thoroughly. Whenever I spray my bags, I double the suggested dry time b/c you just want to make sure it is all dry.