DDG has a stronger commitment to privacy. That said, DDG will almost certainly be outbid by other companies, and DDG will probably face problems scaling to that many users.

It's not only the scaling as a technical problem, but also scaling their Microsoft/Bing relationship.

DDG is effectively outsourcing the search infrastructure to Bing, which puts it in a precarious position.

If DDG becomes the default in Firefox, will Microsoft accept the increased traffic or exposure? Will they keep their current commitment to DDG?

Can you provide source of the claim that DDG search is 'outsourcing the search infrastructure Bing'? This appears to be a regular claim, but as far as I know, DDG buys search data from multiple parties, including Bing, Yandex, and many others. They have their own web crawler as well.

Because outside of Russia's Yandex that works well only in Russia and China's Baidu that works well in China, there's no other alternative. That "etc" in your sentence is not an "et cetera".

Bing is the only game in town for Google alternatives.

Here's a sample of what can happen: https://www.theregister.co.uk/2017/08/15/bing_microsoft_duck...

According to the Wikipedia page at least, DDG claims to have 400 sources and their own crawler. Etc definitely applies.

If you look at the info page by DDG cited in Wikipedia, it'S over 400 sources for the "instant answers" section, not the normal search results, and the phrasing is at least unclear if their own crawler contributes to the normal search results. https://duck.co/help/results/sources

Those other 400 sources probably make up a very small part of the actual search results.