Phenomenal advice - especially about the offset. Thank you!!I'd say base your choice on what you want to do with the stock wheels since the 19's have plenty of sidewall already.
If you like em enough for summer bling bling, keep em and get 18's for the plushier ride.
If you don't want to keep the stockers for summer bling, then, keep them as winter wheels & buy new 19's (or 20's) for summer !
(Careful to get at least 8.5 wide & 35 offset, so the stance is similar, since stock wheels have 8.5 & 29, anything less will be more inward and less aggressive. This is why I went with 9.5 wide & 35 offset, this gives me a 7mm wider stance, and room for 275's once the stock tires are shot.)