The most difficult people I've worked with were not because of technical reasons, but due to reasons outside of that: inability to disagree constructively, unwillingness to compromise, or just general assholes. That kind of stuff.
Someone without the required technical chops can be useless, which isn't good, but these people can be worse than useless as they can derail and/or demoralize an entire team. I've seen it happen; it's not pretty.
This isn't unique to younger people, but in my experience the risk is quite a bit higher in younger people. I say this also as someone who, in hindsight, was quite difficult to work with when I was younger for various reasons. As I've grown older, I've learned a thing or two and I think that now I'm actually a fairly nice person to work with (I hope so, anyway...)
Everything else being equal, I'd rather take someone with a 9 (out of 10) on soft skills and a 6 or 7 on technical skills, than someone with a 3 or 4 on soft skills but a 10 on technical skills.