What are some alternatives?
When comparing phpSitemapNG and VisualSitemaps, you can also consider the following products
DYNO Mapper - Create Sitemaps with the DYNO Mapper Visual Sitemap Generator.
Sitemod - Modify any website in real-time. Share it with the world.
XML-Sitemaps.com - Free Online Google Sitemap Generator.
FlowMapp - UX planning tool for creating a visual sitemap
WonderWebWare Sitemap Generator - Sitemap Generator is freeware program that will help you to automatically generate site maps for google, bing and yahoo in their respective file formats.
MockFlow SiteMap - Create beautiful sitemaps & UI flow