It depends on the article, especially on how popular the topic is. I'd say, in general, that wikipedia articles are more complete than a typical textbook. This is due to space more than anything. A textbook can't spend 1200 words on Julius Caesar's early career before becoming consul. But the rest of his career is pretty comparable to what you might find in a textbook.

Thankfully you do not have to rest on my anecdotal data. Check out this study by Roy Rosenzweig on Wikipedia. This is widely read by teachers and professors and informs many opinions on the website. He concludes that Wikipedia is just as accurate as a comparable encyclopedia, a tad less accurate than a topical encyclopedia, but more exhaustive than either. The issue is that the articles often focus on material that many academics would consider "beside the point" for a person looking for an overview on a topic and its importance to historians.

Edit: the study is about Wikipedia, not at Wikipedia.

James Loewen's Lies My Teacher Told Me is an indictment of the high school history textbook, including on your chosen topic of Christopher Columbus. He'd picked old textbooks and criticized them for outdated scholarship (which is one of several issues I had with his book), but apparently the situation has not improved a whole lot since then.

The problem essentially boils down to a flawed textbook writing system that is based on incremental change that only allows new scholarship to slowly percolate into the books.

Wikipedia pages, at least in theory, can be updated every time a new paper or book comes up.

This is a little bit of an unfair comparison, because most high school textbooks (at least American ones) are pretty terrible, even when they try to get things right. So in areas where Wikipedia articles even have a reasonable stab towards neutrality, recent scholarship, and so forth, they automatically win, hand's down, because the textbooks are so poor.

It's also a bit of an apples-to-oranges comparison because Wikipedia articles are not so limited in brevity as a high school textbook, and brevity is responsible for a lot of the worst aspects of textbooks in my view (when you cannot say much about something, and cannot provide evidence, then you end up with the kind of mealy-mouthed summaries that make textbooks boring and vague).

An example: textbook coverage of the use of the atomic bomb in my experience is limited to a brief account of the end of WWII, a brief framing of the "decision to use the bomb," and then say it was used and the war ended so hurrah. Wikipedia, by comparison, has separate articles about all aspects of this matter, and even discusses the more recent (e.g. last decade or so) historiography of the bomb which has generally rejected the idea that there was a distinct "decision" to use the bomb and has cast doubt on whether the bombs actually were responsible for the Japanese surrender. Now, it's not impossible for a textbook to cover at least some of what it does better (it could, for example, at least acknowledge that the timing of the atomic bombings and the Soviet declaration of war were identical, and the latter may have been at least as influential, if not more so, for the Japanese), but no matter what it does it is going to be a lot more limited in its coverage because it only has maybe one or two paragraphs to devote to the subject, as opposed to Wikipedia's pages and pages.

I think a big difference is Wikipedia encourages you to easily look further at subjects. That was a big part of why I went into history, and also helps the development of history as a long tapestry of interrelated events, not a series of dates to remember.