@MajorAnachronism It may be larger, but it's also generally better. Even just at level 1 (which only requires 3 prize wins compared to 4 for a maxed bridge if you completed all quests in both events) you're gaining % boosts to coin, supply, attack and defense for a small dip in the efficiency of the goods and FP productions. Add in two more prize wins to upgrade the mask vendor and homes and you're now more effective in those two areas as well!
All that being said, comparing sets to buildings that can be motivated isn't entirely even. Sets are vulnerable to plunder and are rather cumbersome to move, but on the flipside don't need to be motivated, which can be a plus for a city that struggles with getting all desired buildings aided.
Anyway, as for the event itself! Based on the beta forums it does sound like the odds of getting a full grand prize for free are relatively low, despite more available florins and cheaper chests. I'll see how it goes once it starts since I have some stuff I'm looking to replace...