$215 will go a long way on the ground, I would go with the cheaper flights and have more spending money. All airlines are pretty similar in economy in terms of food, drink and entertainment. The only caveat to that is, the US airlines have the most senior crews manning these flights so they can be a bit jaded and grumpy.
Eurostar is the way to go between London and Paris. It's more than 20 years since I last flew that route as the eurostar is so much more pleasant. The terminals at either end are also pretty decent.
In terms of price, do use the multi-city options on the usual online travel agencies. June isn't quite peak season for Europe so you might be able to bag yourself a bargain.