Within the EU, there is a 20%~ VAT applied to most things sold. In the US, I think there is a sales tax (% depending on the state) for intra-state trade only. Purely from this perspective, US might seem a better place to do business -- internationally. Look at corporation tax. UK has 20-21%. US has 35%. So that's a cut you give away from your profit before distributing dividends.
You might also want to look at the way the US and UK accept your returns and accounts and their statutory requirements. Definitely things to consider.
Also, keep a close eye on forex. Most companies change with 2-3% commission (banks are way cheaper though). It makes a huge difference.
I'm not an accountant, please correct me if I'm wrong.
A US company incorporated in Delaware would be a good way to go about it. However if you also need a merchant account for the US company for sales then that won't work if the owners are in Netherlands.
It's usually easiest to form your business where you are located, at least at first.
You'll find it's far easier to deal with only one countries tax system as opposed to having to pay a registered agent in an offshore location, having to file taxes in both the Netherlands and in the foreign jurisdiction where you form your business. And that's before we get into the hassle of foreign bank accounts so your foreign business can operate (in other words, plan on traveling to the country where you establish your business to take care of some things).
Form your business locally. VAT rate in the Netherlands is 19% and you won't have to worry about collecting VAT until your sales exceed €104,369 anyway.
Since you aren't physically exporting anything (presumably your electronic files will be downloaded and not shipped on cdroms), you won't need to worry about paying any kind of taxes in the UK or the US unless you establish a presence there.
Long story short: don't worry about trying to evade taxation until you actually have a decent income