Dictionary size is perhaps a poor metric for comparison. An interesting breakdown [1] discusses many different dimensions of language complexities.

A few interesting points:

- 33 unique English words make up 50% of written texts, an d3,000 unique English words make up 95% of English texts. If the notion that 600 French words make up 90% of French texts, does that make French easier or harder than English in this regard (having to know more words, or having to interpret more definitions from context)?

- If you come from a language with gendered nouns, is learning a geographically close language with gendered nouns easier than learning one without gender-specific articles? How does the reverse hold?

- How does regional dialect factor in the language learning? Idioms change in American English from region to region but most words and grammars stay the same. Can the same be said of French, or German? I can drive 100km in Germany and have to say a simple sentence like "I would like apple wine" three very different ways (with, from sight different words) to sound fluent.