There is diminishing returns once you have enough money to spread your message. The problems arise when you don't have a way to spread it at all. It's not always a better funded who wins anyway. The last US election are the prime example: Democrats significantly outspent Trump and lost. I am sure every American have heard both sides as well: their message and their attacks on their opponent. I think more information is better for democracy in general. Removing political ads cuts in in favor of incumbents, who in EU often control other (than the Internet) media.