Good test data. Looks like the advantage of attacking by sea is marginal.
Fluro, you mong war more than I do, but could it be better to attack Paris first? When I attack minor cities first, I lose a few units from suicide siege or attrition, and by the time I heal my units and bombard the capital, the enemy has whipped more defenders. Often I get bogged down and have to declare peace without taking the capital.
Conversely, if I take the capital first, my diminished army can easily handle the smaller cities.
By the way, I think there are some risks to gifting a snowball city for peace. First, gift cities have to be reasonably close to the AI (either by distance or culture, I'm not sure which). The AI won't take just any city you offer it, so we risk settling crap cities that we are unable to give away later. Also, we'd have to sign a peace treaty with 1 city left (ideally accepting techs for peace), then gift a city while we're at peace, then re-attack 10 turns later, capture the last proper city, and then sign cease fire or peace. It's a long time to remain at war, and even longer if the enemy refuses to talk to us.
Remember, when we sign peace, we can't simultaneously accept techs and give away a city ...
EDIT: I see Fluro has addressed this previously:
Another query: Do we know if the AI will always accept an iceball city as a gift? We might be tempted to build one and gift it before the war begins for two reasons: 1. So we can capture all his mainland, and 2. So we get peace earlier to make him build less units.
In the case of de Gaulle, since we're already at war with him we'd have to gift the city now, then re-declare again later (when our army is built up). It will incur an extra permanent "-1 you declared war on us" penalty, but it's possible and may help us build up our army / road in peace.
It hinges on whether we can gift the city successfully.