Trump doesn’t know what he wants, or how to get it. Best case, he gets nothing done; expected case, he does something by accident based on a half-considered remark and it turns out to be something nobody wants.
Clinton, on the other hand, is likely to be “more of the same” — in other words, a general extension of the right-center policies that characterized the Bush and Obama administrations (and indeed Bill Clinton’s). She’s a known quantity, with enough experience to avoid stumbling into a big dumb war.
Clinton is a strong enough leader to execute the plans she has, which are, essentially: avoid pissing off voters, and otherwise change as little as possible. This makes her “conservative” in the traditional sense, and hers is likely to be an uninteresting and unmemorable presidency (like Carter’s).
Trump will either be considered a failure, or will succeed at something that will be considered a huge mistake. A failure would be preferable — but that just brings him down to slightly below Clinton’s expected behavior.