I've found Apple Maps to be absolutely awful. I like the Google UI much better, and I find its navigation, ease of use, and layout to be far superior. I would really love to make it my default.
I don't think I've ever had an issue with Apple Maps interface. It's fairly gorgeous. It's the actual, well, maps that turned me off of it after a few weeks.
When driving I usually use Waze, which doesn't have lane assist and prior to this I used to use a paid version of Tom Tom which did. Don't think it makes a huge difference to me either way.
Having just traveled through the Glasgow, Edinburgh, and London, I can say with confidence that I would have appreciated lane guidance greatly for the 7 million roundabouts I went through.
I didn't know google maps did this or I would have used it. I was using Waze instead, as it's my default.
The website version of google maps is pretty much unusable on an iPhone, I briefly installed the mobile version at some point, but I felt like it was less well integrated overall, so I uninstalled it.