Hi Fede,
There is no particular bike I would recommend. It's just a case of seeing what's available at any given time. In that price range, virtually all the bikes are made in China or Taiwan by large subcontractors so it doesn't make much sense to favour any particular brand, they're all much the same! Years ago we had two 24'' kid's bikes, one a Specialized the other a Scott. It was clear they both came out of the same factory. Most of the parts were exactly the same.