I've incorporated in the UK but I kind of wonder if I made the right choice. It's a fantastic country, but one thing that bothers me and that I discovered too late - only a few weeks ago - is privacy. This is a real one, pay attention to it.
Basically, private companies are as public as american public companies. It's ok to have disclosures to make to the government, but here you also have to disclose your financials to the general public.
Basically with a simple Google Search anyone can know your turnover, your board minutes, but even - more shockingly - your balance sheet, your MONEY IN THE BANK (are you kidding me ?) and the amount you paid yourself as a director among many other things. I find this shocking for companies that are supposed to be private.
After research I've found this is due to European Regulations so it will likely be the same - or quickly be the same - no matter where you go in Europe.
For this very reason, I'd say that if you value privacy, the best place to incorporate a European Web startup is in the US. I'm gutted because I was more than happy to pay my taxes here, this is just a shame.
Then it will of course depends on your focus and your specifics. For me, I am not after exposive growth and investors money, so controlling my disclosures and my image is key to make serious deals with big clients / partners.
I hope my perspective can be somehow useful for you.